Table array with named variables that can contain different types (2024)

Table array with named variables that can contain different types

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Description

table arrays store column-oriented or tabular data, such as columns from a text file or spreadsheet. Tables store each piece of column-oriented data in a variable. Table variables can have different data types and sizes as long as all variables have the same number of rows. Table variables have names, just as the fields of a structure have names. Use the summary function to get information about a table.

To index into a table, use one of these syntaxes. For more information, see Access Data in Tables.

  • Dot notation, as in T.varname, extracts one variable.

  • Curly braces, as in T{rows,vars}, extracts an array from specified rows and variables.

  • Parentheses, as in T(rows,vars), returns a table.

You can perform mathematical operations, such as +, .*, and mean, directly on tables. For more information, see Direct Calculations on Tables and Timetables. (since R2023a)

If your data includes timestamps, consider using a timetable instead.

Creation

You can read data from a file into a table using either the Import Tool or the readtable function. Alternatively, use the table function described below to create a table from input data arrays.

You also can create a table that allows space for variables whose values are filled in later. To create a table with preallocated space for variables, use the table function with 'Size' as the first input argument, as described below.

Syntax

T = table(var1,...,varN)

T = table('Size',sz,'VariableTypes',varTypes)

T = table(___,Name,Value)

T = table

Description

example

T = table(var1,...,varN) creates a table from the input variables var1,...,varN. The variables can have different sizes and data types, but all variables must have the same number of rows.

If the inputs are workspace variables, then table assigns their names as the variable names in the output table. Otherwise, table assigns variable names of the form 'Var1',...,'VarN', where N is the number of variables.

example

T = table('Size',sz,'VariableTypes',varTypes) creates a table and preallocates space for the variables that have data types you specify. sz is a two-element numeric array, where sz(1) specifies the number of rows and sz(2) specifies the number of variables. varTypes specifies the data types of the variables.

example

T = table(___,Name,Value) specifies additional input arguments using one or more name-value pair arguments. For example, you can specify variable names using the 'VariableNames' name-value pair. You can use this syntax with any of the input arguments of the previous syntaxes.

example

T = table creates an empty 0-by-0 table.

Input Arguments

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Input variables, specified as arrays with the same number of rows. The input variables can have different sizes and different data types.

Common input variables are numeric arrays, logical arrays, character arrays, structure arrays, or cell arrays. Input variables also can be objects that are arrays. Such an array must support indexing of the form var(index1,...,indexN), where index1 is a numeric or logical vector that corresponds to rows of the variable var. In addition, the array must implement both a vertcat method and a size method with a dim argument.

Example: table([1:4]',ones(4,3,2),eye(4,2)) creates a table from variables with four rows, but different sizes.

Example: table([1:3]',{'one';'two';'three'},categorical({'A';'B';'C'})) creates a table from variables with three rows, but different data types.

Size of the preallocated table, specified as a two-element numeric vector. The first element of sz specifies the number of rows, and the second element specifies the number of table variables.

To create variables only, without any rows, specify 0 as the first element of sz.

Example: T = table('Size',[50 3],'VariableTypes',{'string','double','datetime'}) preallocates 50 rows for a table that contains a string array, a double array, and a datetime array.

Example: T = table('Size',[0 4],'VariableTypes',varTypes) specifies zero rows and four variables.

Data types of the preallocated variables, specified as a cell array of character vectors or a string array. The number of types specified by varTypes must equal the number of variables specified by the second element of sz.

varTypes can contain the names of any data types, including the names shown in the table.

Data Type Name

Initial Value in Each Element

'double','single'

Double- or single-precision 0

'doublenan', 'doubleNaN','singlenan', 'singleNaN'

Double- or single-precision NaN

'int8','int16','int32','int64'

Signed 8-, 16-, 32-, or 64-bit integer 0

'uint8','uint16','uint32','uint64'

Unsigned 8-, 16-, 32-, or 64-bit integer 0

'logical'

0 (false)

'categorical'

<undefined> categorical value

'datetime'

NaT datetime value

'duration'

0 seconds, as a duration value

'calendarDuration'

0 days, as a calendarDuration value

'string'

<missing> (missing string)

'cellstr'

{''} (cell with 0-by-0 character array)

'cell'

{[]} (cell with 0-by-0 double array)

'struct'

Scalar structure with no fields

'table'

Table with no variables

'timetable'

Timetable with no variables and NaT for row times

For any other data type, the initial value is the value used by that type or class to "in-fill" unassigned elements of an array.

If you specify 'char' as a data type, then table preallocates the corresponding variable as a cell array of character vectors, not as a character array. Best practice is to avoid creating table or timetable variables that are character arrays. When working with text data in a table or a timetable, consider using a string array or a categorical array.

Name-Value Arguments

Specify optional pairs of arguments as Name1=Value1,...,NameN=ValueN, where Name is the argument name and Value is the corresponding value. Name-value arguments must appear after other arguments, but the order of the pairs does not matter.

Before R2021a, use commas to separate each name and value, and enclose Name in quotes.

Example: T = table(Age,Height,Weight,'RowNames',LastName) creates a table with row names that are specified by the variable LastName.

Variable names, specified as a cell array of character vectors or a string array whose elements are nonempty and distinct.

  • The number of names in the array must equal the number of table variables.

  • The table function also stores the variable names in the VariableNames property of the table.

  • Variable names can have any Unicode® characters, including spaces and non-ASCII characters.

Example: T = table(lat,lon,'VariableNames',["Latitude","Longitude"]) creates a table from input arrays lat and lon, and names the corresponding table variables Latitude and Longitude.

Row names, specified as a cell array of character vectors or a string array whose elements are nonempty and distinct.

  • The number of names in the array must equal the number of rows.

  • The table function also stores the row names in the RowNames property of the table.

  • Row names can have any Unicode characters, including spaces and non-ASCII characters.

  • The table function removes any leading or trailing whitespace characters from the row names.

Example: T = table(Age,Height,Weight,'RowNames',LastName) creates a table with row names that are specified by the variable LastName.

Since R2021a

Dimension names, specified as a two-element cell array of character vectors or two-element string array whose elements are nonempty and distinct.

  • The table function also stores the dimension names in the DimensionNames property of the table.

  • Dimension names can have any Unicode characters, including spaces and non-ASCII characters.

Before R2021a, you can specify dimension names only by setting the DimensionNames property.

Example: T = table(Age,Height,Weight,'RowNames',LastName,'DimensionNames',["PatientName","PatientData"]) creates a table where the name of the first dimension is "PatientName" and the name of the second dimension is "PatientData".

Properties

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Access Table Metadata Properties

A table contains metadata properties that describe the table and its variables. Access these properties using the syntax tableName.Properties.PropertyName, where PropertyName is the name of a property. For example, you can access the names of the variables in table T using the syntax T.Properties.VariableNames.

You can return a summary of all the metadata properties using the syntax tableName.Properties.

Tables provide metadata access through the Properties property because you can access table data directly using dot syntax. For example, if table T has a variable named Var1, then you can access the values in the variable by using the syntax T.Var1.

Table Metadata

Dimension names, specified as a two-element cell array of character vectors or a two-element string array.

  • Dimension names can have any Unicode characters, including spaces and non-ASCII characters.

  • If you specify this property using a string array, then it is converted and stored as a cell array of character vectors.

You can access table data using the two dimension names.

  • If the table has row names, and you use dot syntax and the first dimension name, then you can access the row names as a vector.

  • If you use dot syntax and the second dimension name, then the data from all the variables are concatenated together in one array, as though you had indexed into the table using {:,:} syntax.

Example

Create a table and display its dimension names. You can access row names and data using dimension names with dot syntax.

load patientsT = table(Age,Height,Weight,Systolic,Diastolic, ... 'RowNames',LastName);T.Properties.DimensionNames
ans = 1x2 cell {'Row'} {'Variables'}

Access the row names using the first dimension name. Display the first five names.

T.Row(1:5)
ans = 5x1 cell {'Smith' } {'Johnson' } {'Williams'} {'Jones' } {'Brown' }

Access the data using the second dimension name. This syntax is equivalent to T{:,:}.

T.Variables
ans = 100×5 38 71 176 124 93 43 69 163 109 77 38 64 131 125 83 40 67 133 117 75 49 64 119 122 80 46 68 142 121 70 33 64 142 130 88 40 68 180 115 82 28 68 183 115 78 31 66 132 118 86 ⋮

Modify the names of its dimensions using the Properties.DimensionNames property. Having changed the dimension names, you can access the row names and data using the syntaxes T.Patient and T.Data respectively.

T.Properties.DimensionNames = ["Patient","Data"];T.Properties
ans = TableProperties with properties: Description: '' UserData: [] DimensionNames: {'Patient' 'Data'} VariableNames: {'Age' 'Height' 'Weight' 'Systolic' 'Diastolic'} VariableDescriptions: {} VariableUnits: {} VariableContinuity: [] RowNames: {100x1 cell} CustomProperties: No custom properties are set. Use addprop and rmprop to modify CustomProperties.

Row names, specified as a cell array of character vectors or a string array whose elements are nonempty and distinct. If RowNames is not empty, then the number of row names must equal the number of rows in the table.

  • Row names can have any Unicode characters, including spaces and non-ASCII characters.

  • If you assign row names with leading or trailing whitespace characters, then MATLAB® removes them from the row names.

  • The row names are visible when you view the table. Furthermore, you can use the row names within parentheses or curly braces to access the table data.

  • Another way to access the row names is to use dot syntax and the name of the first dimension of the table.

  • If you specify this property using a string array, then it is converted and stored as a cell array of character vectors.

Example

Create a table. Then add row names and access rows by their names.

load patientsT = table(Age,Height,Weight,Smoker,Systolic,Diastolic,SelfAssessedHealthStatus);T.SelfAssessedHealthStatus = string(SelfAssessedHealthStatus);

Add row names using the Properties.RowNames property. By default, tables do not have row names, but you can add them at any time.

 Age Height Weight Smoker Systolic Diastolic SelfAssessedHealthStatus ___ ______ ______ ______ ________ _________ ________________________ Smith 38 71 176 true 124 93 "Excellent" Johnson 43 69 163 false 109 77 "Fair" Williams 38 64 131 false 125 83 "Good" Jones 40 67 133 false 117 75 "Fair" Brown 49 64 119 false 122 80 "Good"

Another way to access the row names is by using dot syntax with the name of the first dimension of the table. Display the first five row names.

T.Properties.DimensionNames
ans = 1x2 cell {'Row'} {'Variables'}
T.Row(1:5)
ans = 5x1 cell {'Smith' } {'Johnson' } {'Williams'} {'Jones' } {'Brown' }

Index into the table by row names.

T(["Smith","Brown"],:)
ans=2×7 table Age Height Weight Smoker Systolic Diastolic SelfAssessedHealthStatus ___ ______ ______ ______ ________ _________ ________________________ Smith 38 71 176 true 124 93 "Excellent" Brown 49 64 119 false 122 80 "Good"

Table description, specified as a character vector or string scalar. This description is visible when using the summary function.

If you specify this property using a string scalar, then it is converted and stored as a character vector.

Example

Create a table. Modify the description of the table. Display a summary of the result.

load patientsT = table(LastName,Age,Height,Weight);T.LastName = string(T.LastName);T.Properties.Description = "Simulated patient data";summary(T)
Description: Simulated patient dataVariables: LastName: 100x1 string Age: 100x1 double Values: Min 25 Median 39 Max 50 Height: 100x1 double Values: Min 60 Median 67 Max 72 Weight: 100x1 double Values: Min 111 Median 142.5 Max 202

Additional table information, specified as an array. You can attach data of any kind to a table using this property.

Example

Create a table. Attach an anonymous function as a piece of user data that is associated with the table.

load patientsT = table(LastName,Age,Height,Weight,Smoker,Systolic,Diastolic);formula = @(x) x.^2;T.Properties.UserData = formula;T.Properties
ans = TableProperties with properties: Description: '' UserData: @(x)x.^2 DimensionNames: {'Row' 'Variables'} VariableNames: {'LastName' 'Age' 'Height' 'Weight' 'Smoker' 'Systolic' 'Diastolic'} VariableDescriptions: {} VariableUnits: {} VariableContinuity: [] RowNames: {} CustomProperties: No custom properties are set. Use addprop and rmprop to modify CustomProperties.

Variable Metadata

Variable names, specified as a cell array of character vectors or a string array whose elements are nonempty and distinct. The number of names must equal the number of variables.

  • Variable names can have any Unicode characters, including spaces and non-ASCII characters.

  • The variable names are visible when viewing the table and when using the summary function. Furthermore, you can use the variable names within parentheses, within curly braces, or with dot indexing to access table data.

  • If you specify this property using a string array, then it is converted and stored as a cell array of character vectors.

Example

Create a table with default variable names. Then modify the names using the Properties.VariableNames property.

T = table(["Smith";"Nguyen";"Williams";"Fernandez";"Brown"],[38;43;38;40;49], ... [71;69;64;67;64],[176;163;131;133;119])
T=5×4 table Var1 Var2 Var3 Var4 ___________ ____ ____ ____ "Smith" 38 71 176 "Nguyen" 43 69 163 "Williams" 38 64 131 "Fernandez" 40 67 133 "Brown" 49 64 119 
T.Properties.VariableNames = ["LastName","Age","Height","Weight"]
T=5×4 table LastName Age Height Weight ___________ ___ ______ ______ "Smith" 38 71 176 "Nguyen" 43 69 163 "Williams" 38 64 131 "Fernandez" 40 67 133 "Brown" 49 64 119

A fundamental way to display and modify variables is to access them by name using dot syntax.

T.Age
ans = 5×1 38 43 38 40 49
T.Age(1) = 53
T=5×4 table LastName Age Height Weight ___________ ___ ______ ______ "Smith" 53 71 176 "Nguyen" 43 69 163 "Williams" 38 64 131 "Fernandez" 40 67 133 "Brown" 49 64 119

Variable descriptions, specified as a cell array of character vectors or a string array This property can be an empty cell array, which is the default. If the array is not empty, then it must contain as many elements as there are variables. You can specify an individual empty character vector or empty string for a variable that does not have a description.

  • The variable descriptions are visible when using the summary function.

  • If you specify this property using a string array, then it is converted and stored as a cell array of character vectors.

Example

Create a table. Modify the variable descriptions. Display a summary of the result.

load patientsT = table(LastName,Age,Height,Weight,Smoker,Systolic,Diastolic);T.LastName = string(T.LastName);T.Properties.VariableDescriptions = ["","","","", ... "Has the patient ever been a smoker", ... "Systolic Pressure","Diastolic Pressure"];summary(T)
Variables: LastName: 100x1 string Age: 100x1 double Values: Min 25 Median 39 Max 50 Height: 100x1 double Values: Min 60 Median 67 Max 72 Weight: 100x1 double Values: Min 111 Median 142.5 Max 202 Smoker: 100x1 logical Properties: Description: Has the patient ever been a smoker Values: True 34 False 66 Systolic: 100x1 double Properties: Description: Systolic Pressure Values: Min 109 Median 122 Max 138 Diastolic: 100x1 double Properties: Description: Diastolic Pressure Values: Min 68 Median 81.5 Max 99

Variable units, specified as a cell array of character vectors or a string array. This property can be an empty cell array, which is the default. If the array is not empty, then it must contain as many elements as there are variables. You can specify an individual empty character vector or empty string for a variable that does not have units.

  • The variable units are visible when using the summary function.

  • If you specify this property using a string array, then it is converted and stored as a cell array of character vectors.

Example

Create a table. Modify the variable units. Display a summary of the result.

load patientsT = table(LastName,Age,Height,Weight,Smoker,Systolic,Diastolic);T.LastName = string(T.LastName);T.Properties.VariableUnits = ["","Yrs","In","Lbs","","mm Hg","mm Hg"];summary(T)
Variables: LastName: 100x1 string Age: 100x1 double Properties: Units: Yrs Values: Min 25 Median 39 Max 50 Height: 100x1 double Properties: Units: In Values: Min 60 Median 67 Max 72 Weight: 100x1 double Properties: Units: Lbs Values: Min 111 Median 142.5 Max 202 Smoker: 100x1 logical Values: True 34 False 66 Systolic: 100x1 double Properties: Units: mm Hg Values: Min 109 Median 122 Max 138 Diastolic: 100x1 double Properties: Units: mm Hg Values: Min 68 Median 81.5 Max 99

Status as continuous or discrete variables, specified as a cell array of character vectors or a string array.

While tables and timetables both have this property, only timetables use it. For more information, see the VariableContinuity property of timetable.

Custom Metadata

Customized metadata of a table and its variables, specified as a CustomProperties object.

The CustomProperties object is a container for customized metadata that you can add to a table. By default, CustomProperties has zero properties. Each property you add to CustomProperties can contain either table metadata or variable metadata. If a property contains variable metadata, then its value must be an array, and the number of elements in the array must equal the number of table variables.

  • To add properties for customized metadata to a table, use the addprop function.

  • To access or modify customized metadata, use the syntax tableName.Properties.CustomProperties.PropertyName. In this syntax, PropertyName is the name you chose when you added that property using addprop.

  • To remove properties, use the rmprop function.

Note: You can add or remove only properties for customized metadata using addprop and rmprop. You cannot add or remove properties of the tableName.Properties object.

Example

Create a table.

load patientsT = table(LastName,Age,Height,Weight,Smoker,Systolic,Diastolic);

Add properties that can hold customized metadata about the table and its variables. In this example, the metadata are names of instruments, true and false values indicating whether variables are to be plotted, and the name of an output file. To add properties, use the addprop function.

T = addprop(T,["Instrument","ToPlot","OutputFile"],["variable","variable","table"]);T.Properties
ans = TableProperties with properties: Description: '' UserData: [] DimensionNames: {'Row' 'Variables'} VariableNames: {'LastName' 'Age' 'Height' 'Weight' 'Smoker' 'Systolic' 'Diastolic'} VariableDescriptions: {} VariableUnits: {} VariableContinuity: [] RowNames: {} Custom Properties (access using t.Properties.CustomProperties.<name>): OutputFile: [] Instrument: [] ToPlot: []

Assign values to the customized metadata using dot syntax. When you assign an array of text values to customized metadata, the best practice is to use a string array, not a cell array of character vectors. If a property of CustomProperties is a cell array of character vectors, then there is no mechanism to prevent you from later assigning nontext values as elements of the cell array.

T.Properties.CustomProperties.Instrument = ["","","height rod","scale","","blood pressure cuff","blood pressure cuff"];T.Properties.CustomProperties.ToPlot = [false false true true false true true];T.Properties.CustomProperties.OutputFile = 'patientData.csv';T.Properties
ans = TableProperties with properties: Description: '' UserData: [] DimensionNames: {'Row' 'Variables'} VariableNames: {'LastName' 'Age' 'Height' 'Weight' 'Smoker' 'Systolic' 'Diastolic'} VariableDescriptions: {} VariableUnits: {} VariableContinuity: [] RowNames: {} Custom Properties (access using t.Properties.CustomProperties.<name>): OutputFile: 'patientData.csv' Instrument: ["" "" "height rod" "scale" "" "blood pressure cuff" "blood pressure cuff"] ToPlot: [0 0 1 1 0 1 1]

Remove the OutputFile property from T.

T = rmprop(T,"OutputFile");T.Properties
ans = TableProperties with properties: Description: '' UserData: [] DimensionNames: {'Row' 'Variables'} VariableNames: {'LastName' 'Age' 'Height' 'Weight' 'Smoker' 'Systolic' 'Diastolic'} VariableDescriptions: {} VariableUnits: {} VariableContinuity: [] RowNames: {} Custom Properties (access using t.Properties.CustomProperties.<name>): Instrument: ["" "" "height rod" "scale" "" "blood pressure cuff" "blood pressure cuff"] ToPlot: [0 0 1 1 0 1 1]

Examples

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Store Related Data Variables in Table

Open Live Script

Store data about a group of patients in a table. You can perform calculations and store results in the same table. Also, you can annotate the table to describe your work and the variables of the table.

First, create workspace variables that have the patient data. The variables can have any data types but must have the same number of rows.

LastName = {'Sanchez';'Johnson';'Li';'Diaz';'Brown'};Age = [38;43;38;40;49];Smoker = logical([1;0;1;0;1]);Height = [71;69;64;67;64];Weight = [176;163;131;133;119];BloodPressure = [124 93; 109 77; 125 83; 117 75; 122 80];

Create a table, T, as a container for the workspace variables. The table function uses the workspace variable names as the names of the table variables in T. A table variable can have multiple columns. For example, the BloodPressure variable in T is a 5-by-2 array.

T = table(LastName,Age,Smoker,Height,Weight,BloodPressure)
T=5×6 table LastName Age Smoker Height Weight BloodPressure ___________ ___ ______ ______ ______ _____________ {'Sanchez'} 38 true 71 176 124 93 {'Johnson'} 43 false 69 163 109 77 {'Li' } 38 true 64 131 125 83 {'Diaz' } 40 false 67 133 117 75 {'Brown' } 49 true 64 119 122 80

You can use dot indexing to access table variables. For example, calculate the mean height of the patients using the values in T.Height.

meanHeight = mean(T.Height)

Calculate body mass index (BMI), and add it as a new table variable. You also can add and name table variables in one step, using dot syntax.

T.BMI = (T.Weight*0.453592)./(T.Height*0.0254).^2
T=5×7 table LastName Age Smoker Height Weight BloodPressure BMI ___________ ___ ______ ______ ______ _____________ ______ {'Sanchez'} 38 true 71 176 124 93 24.547 {'Johnson'} 43 false 69 163 109 77 24.071 {'Li' } 38 true 64 131 125 83 22.486 {'Diaz' } 40 false 67 133 117 75 20.831 {'Brown' } 49 true 64 119 122 80 20.426

Annotate the table with a description of the BMI calculation. You can annotate T and its variables using metadata accessed through T.Properties.

T.Properties.Description = 'Patient data, including body mass index (BMI) calculated using Height and Weight';T.Properties
ans = TableProperties with properties: Description: 'Patient data, including body mass index (BMI) calculated using Height and Weight' UserData: [] DimensionNames: {'Row' 'Variables'} VariableNames: {'LastName' 'Age' 'Smoker' 'Height' 'Weight' 'BloodPressure' 'BMI'} VariableDescriptions: {} VariableUnits: {} VariableContinuity: [] RowNames: {} CustomProperties: No custom properties are set. Use addprop and rmprop to modify CustomProperties.

Access All Table Data as Matrix

Open Live Script

Access all the data from a table as a matrix, using the name of the second dimension of the table.

Create a table that has five rows of data about a set of patients.

Age = [38;43;38;40;49];Smoker = logical([1;0;1;0;1]);Height = [71;69;64;67;64];Weight = [176;163;131;133;119];BloodPressure = [124 93; 109 77; 125 83; 117 75; 122 80];T = table(Age,Smoker,Height,Weight,BloodPressure)
T=5×5 table Age Smoker Height Weight BloodPressure ___ ______ ______ ______ _____________ 38 true 71 176 124 93 43 false 69 163 109 77 38 true 64 131 125 83 40 false 67 133 117 75 49 true 64 119 122 80

Display the names of the table dimensions using the DimensionNames property. The default name of the second dimension is Variables.

T.Properties.DimensionNames
ans = 1x2 cell {'Row'} {'Variables'}

Access the table data as a matrix using the syntax T.Variables. This syntax is equivalent to accessing all the contents using curly brace syntax, T{:,:}. If the table data cannot be concatenated into a matrix, then an error message is raised.

T.Variables
ans = 5×6 38 1 71 176 124 93 43 0 69 163 109 77 38 1 64 131 125 83 40 0 67 133 117 75 49 1 64 119 122 80

Rename the second dimension. If you change the name, then you can use the new name to access the data.

T.Properties.DimensionNames{2} = 'PatientData';T.PatientData
ans = 5×6 38 1 71 176 124 93 43 0 69 163 109 77 38 1 64 131 125 83 40 0 67 133 117 75 49 1 64 119 122 80

Specify Size and Variable Types

Open Live Script

Preallocate a table by specifying its size and the data types of the variables. The table function fills the variables with default values that are appropriate for the data types you specify. It also gives the variables default names, but you also can assign variable names of your own. Preallocation provides room for data you add to the table later.

sz = [4 3];varTypes = {'double','datetime','string'};T = table('Size',sz,'VariableTypes',varTypes)
T=4×3 table Var1 Var2 Var3 ____ ____ _________ 0 NaT <missing> 0 NaT <missing> 0 NaT <missing> 0 NaT <missing>

To specify names for the variables, use the 'VariableNames' name-value pair argument.

varNames = {'Temperature','Time','Station'};T2 = table('Size',sz,'VariableTypes',varTypes,'VariableNames',varNames)
T2=4×3 table Temperature Time Station ___________ ____ _________ 0 NaT <missing> 0 NaT <missing> 0 NaT <missing> 0 NaT <missing>

Add rows of data to the first two rows of T2. Preallocation can be a useful technique when your code adds one row of data, or a few rows of data, at a time. Instead of growing the table every time you add a row, you can fill in table variables that already have room for your data.

T2(1,:) = {75,datetime('now'),"S1"};T2(2,:) = {68,datetime('now')+1,"S2"}
T2=4×3 table Temperature Time Station ___________ ____________________ _________ 75 12-Feb-2024 22:34:34 "S1" 68 13-Feb-2024 22:34:34 "S2" 0 NaT <missing> 0 NaT <missing>

You can encapsulate a row of data values in a cell array. When you assign a row from a cell array, elements from the cell array are assigned to the row in the table.

Specify Variable Names

Open Live Script

Create a table from arrays. To specify table variable names, use the 'VariableNames' name-value pair argument. For example, you can use 'VariableNames' to specify names when the other input arguments are not workspace variables.

T = table(categorical({'M';'F';'M'}),[45;32;34],... {'NY';'CA';'MA'},logical([1;0;0]),... 'VariableNames',{'Gender','Age','State','Vote'})
T=3×4 table Gender Age State Vote ______ ___ ______ _____ M 45 {'NY'} true F 32 {'CA'} false M 34 {'MA'} false

Create a table with the state names as row names. You can specify both the 'VariableNames' and 'RowNames' name-value pairs when using the table function.

T = table(categorical({'M';'F';'M'}),[45;32;34],logical([1;0;0]),... 'VariableNames',{'Gender','Age','Vote'},... 'RowNames',{'NY';'CA';'MA'})
T=3×3 table Gender Age Vote ______ ___ _____ NY M 45 true CA F 32 false MA M 34 false

Specify Row Names

Open Live Script

Specify row names for a table. Tables do not have to have row names, but if you specify them, then you can index into a table by row name. You also can access the set of row names using the name of the first dimension of a table.

Create arrays containing patient data.

LastName = {'Sanchez';'Johnson';'Lee';'Diaz';'Brown'};Age = [38;43;38;40;49];Height = [71;69;64;67;64];Weight = [176;163;131;133;119];

Create a table containing the arrays. Specify LastName as the source of row names for the table. The table has only three variables. The row names are not a table variable, but instead a property of the table.

T = table(Age,Weight,Height,'RowNames',LastName)
T=5×3 table Age Weight Height ___ ______ ______ Sanchez 38 176 71 Johnson 43 163 69 Lee 38 131 64 Diaz 40 133 67 Brown 49 119 64

Since the rows have row names, you can index into the rows of T by name.

T('Lee',:)
ans=1×3 table Age Weight Height ___ ______ ______ Lee 38 131 64

To specify multiple rows, use a cell array.

T({'Lee','Brown'},:)
ans=2×3 table Age Weight Height ___ ______ ______ Lee 38 131 64 Brown 49 119 64

To access all the row names of T as a cell array, use the syntax T.Row. By default, Row is the name of the first dimension of a table.

T.Row
ans = 5x1 cell {'Sanchez'} {'Johnson'} {'Lee' } {'Diaz' } {'Brown' }

Change the name of the first dimension. If you change the name, then you can access the row names using the new name.

T.Properties.DimensionNames{1} = 'LastNames';T.LastNames
ans = 5x1 cell {'Sanchez'} {'Johnson'} {'Lee' } {'Diaz' } {'Brown' }

Specify Table Variables and Row Names Using String Arrays

Open Live Script

Starting in R2017a, you can create strings using double quotes, and add string arrays as table variables.

FlightNum = [1261;547;3489];Customer = ["Jones";"Brown";"Smith"];Date = datetime(2016,12,20:22)';Rating = categorical(["Good";"Poor";"Fair"]);Comment = ["Flight left on time, not crowded";... "Late departure, ran out of dinner options";... "Late, but only by half an hour. Otherwise fine."];T = table(FlightNum,Customer,Date,Rating,Comment)
T=3×5 table FlightNum Customer Date Rating Comment _________ ________ ___________ ______ _________________________________________________ 1261 "Jones" 20-Dec-2016 Good "Flight left on time, not crowded" 547 "Brown" 21-Dec-2016 Poor "Late departure, ran out of dinner options" 3489 "Smith" 22-Dec-2016 Fair "Late, but only by half an hour. Otherwise fine."

To use the text in a string array as row names, convert the string array to a cell array of character vectors. Then create a table with row names.

Customer = cellstr(Customer);T = table(FlightNum,Date,Rating,Comment,'RowNames',Customer)
T=3×4 table FlightNum Date Rating Comment _________ ___________ ______ _________________________________________________ Jones 1261 20-Dec-2016 Good "Flight left on time, not crowded" Brown 547 21-Dec-2016 Poor "Late departure, ran out of dinner options" Smith 3489 22-Dec-2016 Fair "Late, but only by half an hour. Otherwise fine."

Build Table by Assigning Variables Individually

Open Live Script

Create workspace variables containing snowfall totals on different dates at three locations. These variables are row vectors.

Date = {'12/25/11','1/2/12','1/23/12','2/7/12','2/15/12'};location1 = [20 5 13 0 17];location2 = [18 9 21 5 12];location3 = [26 10 16 3 15];

One way to create a table from these variables is to call the table function with the syntax T = table(Date',location1',location2',location3'). Because the workspace variables are row vectors, you must transpose them to put them into the table as column-oriented data. Therefore, the input arguments are expressions, not simple variables. As a result, table creates T with the default variable names Var1, Var2, Var3, and Var4. You can assign more meaningful names to T.Properties.VariableNames after you create T. But, it might be more convenient to create an empty table, and then add variables one at a time with new names.

Create an empty table. Transpose the workspace variables and add them to the table as column vectors. As part of assigning each workspace variable into T, provide a meaningful name for the table variable.

T = table;T.Date = Date';T.Natick = location1';T.Boston = location2';T.Worcester = location3'
T=5×4 table Date Natick Boston Worcester ____________ ______ ______ _________ {'12/25/11'} 20 18 26 {'1/2/12' } 5 9 10 {'1/23/12' } 13 21 16 {'2/7/12' } 0 5 3 {'2/15/12' } 17 12 15

Specify Variable Names Using Any Characters

Open Live Script

Starting in R2019b, you can specify table variable names that are not valid MATLAB® identifiers. Such variable names can include spaces, non-ASCII characters, and can have any character as the leading character. When you access such a variable name, enclose it quotation marks.

Create a table that stores data about a set of patients. Start with their ages and status as smokers.

Age = [38;43;38;40;49];Smoker = logical([1;0;1;0;1]);Height = [71;69;64;67;64];Weight = [176;163;131;133;119];BloodPressure = [124 93; 109 77; 125 83; 117 75; 122 80];T = table(Age,Smoker)
T=5×2 table Age Smoker ___ ______ 38 true 43 false 38 true 40 false 49 true

Add the blood pressure readings with the variable name '29-May-2019 Blood Pressure Reading'. You can use dot syntax to add or access the variable. Since its name is not a valid MATLAB identifier, use parentheses and quotation marks with dot syntax.

T.('29-May-2019 Blood Pressure Reading') = BloodPressure
T=5×3 table Age Smoker 29-May-2019 Blood Pressure Reading ___ ______ __________________________________ 38 true 124 93 43 false 109 77 38 true 125 83 40 false 117 75 49 true 122 80

When table variable names are valid MATLAB identifiers, you can use dot syntax without parentheses and quotation marks.

T.Height = Height;T.Weight = Weight
T=5×5 table Age Smoker 29-May-2019 Blood Pressure Reading Height Weight ___ ______ __________________________________ ______ ______ 38 true 124 93 71 176 43 false 109 77 69 163 38 true 125 83 64 131 40 false 117 75 67 133 49 true 122 80 64 119

Index into T using variable names.

T(:,{'Age','Smoker','29-May-2019 Blood Pressure Reading'})
ans=5×3 table Age Smoker 29-May-2019 Blood Pressure Reading ___ ______ __________________________________ 38 true 124 93 43 false 109 77 38 true 125 83 40 false 117 75 49 true 122 80

Limitations

  • Use single quotes for these input names:

    • 'DimensionNames' (since R2021a)

    • 'RowNames'

    • 'Size'

    • 'VariableTypes'

    • 'VariableNames'

    To avoid confusion with variable inputs, do not use double-quoted string scalars (such as "RowNames") for these names.

Tips

  • For a list of functions that accept or return tables, see Tables.

Extended Capabilities

Thread-Based Environment
Run code in the background using MATLAB® backgroundPool or accelerate code with Parallel Computing Toolbox™ ThreadPool.

Version History

Introduced in R2013b

expand all

MATLAB raises an error if you assign a dimension name that matches one of these reserved names: 'Properties', 'RowNames', 'VariableNames', or ':'. In previous releases, MATLAB raised a warning and modified the dimension names so that they were different from the reserved names.

MATLAB raises an error if you assign a table variable name that matches a dimension name, or a dimension name that matches a variable name. In previous releases, MATLAB raised a warning and modified the names so they were unique.

See Also

readtable | cell2table | array2table | struct2table | isvarname | summary | uitable | tall

Topics

  • Create Tables and Assign Data to Them
  • Rename and Describe Table Variables
  • Access Data in Tables
  • Calculations When Tables Have Both Numeric and Nonnumeric Data

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