Determine whether array uses complex storage
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Syntax
tf = isreal(A)
Description
example
tf = isreal(A) returns logical 1 (true) when numeric array A does not have an imaginary part, and logical 0 (false) otherwise. isreal returns logical 0 (false) for complex values that have zero imaginary part, since the value is still stored as a complex number.
Examples
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Determine Whether Matrix Contains All Real Values
Open Live Script
Define a 3-by-4 matrix, A.
A = [7 3+4i 2 5i;... 2i 1+3i 12 345;... 52 108 78 3];
Determine whether the array is real.
tf = isreal(A)
tf = logical 0Since A contains complex elements, isreal returns false.
Define Complex Number with Zero-Valued Imaginary Part
Open Live Script
Use the complex function to create a scalar, A, with zero-valued imaginary part.
A = complex(12)
A = 12.0000 + 0.0000i
Determine whether A is real.
tf = isreal(A)
tf = logical 0A is not real because it has an imaginary part, even though the value of the imaginary part is 0.
Determine whether A contains any elements with zero-valued imaginary part.
~any(imag(A))
ans = logical 1A contains elements with zero-valued imaginary part.
Computation Resulting in Zero-Valued Imaginary Part
Open Live Script
Define two complex scalars, x and y.
x=3+4i;y=5-4i;
Determine whether the addition of two complex scalars, x and y, is real.
A = x+y
MATLAB® drops the zero imaginary part.
isreal(A)
ans = logical 1A is real since it does not have an imaginary part.
Find Real Elements in Cell Array
Open Live Script
Create a cell array.
C{1,1} = pi; % doubleC{2,1} = 'John Doe'; % char arrayC{3,1} = 2 + 4i; % complex doubleC{4,1} = ispc; % logicalC{5,1} = magic(3); % double arrayC{6,1} = complex(5,0) % complex doubleC=6×1 cell array {[ 3.1416]} {'John Doe' } {[2.0000 + 4.0000i]} {[ 0]} {3x3 double } {[5.0000 + 0.0000i]}C is a 1-by-6 cell array.
Loop over the elements of a cell array to distinguish between real and complex elements.
for k = 1:6x(k,1) = isreal(C{k,1});endx
x = 6x1 logical array 1 1 0 1 1 0All but C{3,1} and C{6,1} are real arrays.
Input Arguments
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A — Input array
scalar | vector | matrix | multidimensional array
Input array, specified as a scalar, vector, matrix, or multidimensionalarray.
For numeric data types, if
Adoesnot have an imaginary part,isrealreturnstrue;ifAdoes have an imaginary partisrealreturnsfalse.For
duration,calendarDuration,logical, andchardata types,isrealalways returnstrue.For
string,table,cell,struct,datetime,function_handle, andobjectdata types,isrealalways returnsfalse.
Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | logical | char | string | struct | table | cell | datetime | duration | calendarDuration | function_handle
Complex Number Support: Yes
Tips
To check whether each element of an array
Ais real, useA == real(A).isreal(complex(A))always returnsfalse,even when the imaginary part is all zeros.~isreal(x)detects arrays thathave an imaginary part, even if it is all zeros.
Extended Capabilities
C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.
GPU Code Generation
Generate CUDA® code for NVIDIA® GPUs using GPU Coder™.
HDL Code Generation
Generate VHDL, Verilog and SystemVerilog code for FPGA and ASIC designs using HDL Coder™.
Thread-Based Environment
Run code in the background using MATLAB® backgroundPool or accelerate code with Parallel Computing Toolbox™ ThreadPool.
This function fully supports thread-based environments. For more information, see Run MATLAB Functions in Thread-Based Environment.
GPU Arrays
Accelerate code by running on a graphics processing unit (GPU) using Parallel Computing Toolbox™.
This function fully supports GPU arrays. For more information, see Run MATLAB Functions on a GPU (Parallel Computing Toolbox).
Distributed Arrays
Partition large arrays across the combined memory of your cluster using Parallel Computing Toolbox™.
This function fully supports distributed arrays. For more information, see Run MATLAB Functions with Distributed Arrays (Parallel Computing Toolbox).
Version History
Introduced before R2006a
See Also
complex | isnumeric | isnan | isprime | isfinite | isinf | isa
Topics
- Create Complex Numbers
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