Add headers to matrix using table (2024)

+1

I would recommend not to use white space in variable names of a table variable.

The following would be one possible solution:

Great answer! Thanks for helping me out. The string class feature opened my eyes. I am new to matlab, and I am impressed by how conscise a loop can be here. With this improvement, the codes are much clearer.

As for the trouble shoot, seems like I still have a lot of work to do about the classes. Do you have any reading recommendations about the classes, such as table, cell, arrays? I am a bit lost here.

Thanks again for the help.

Cool code. I am spending a lot of time to wrap my head around it. You helped me to optimize my codes a lot. 3 questions here.

1. for this loop, how did the cell structure work?

I am seeing the content of the right side transfered to the content of the left side?

also, the content of "data" is a cell contenting an array, and it was transfered to sepeate cells in "tData". I am lost.

2. for this statement,

why should we put an "@" to the function name? I tried to delete the sign and it doesn't work.

3. Generally, I see that you read the file into an array into cells, then transfer the data to cells individually, and work with the table. Can you read the data into the table directly using readtable function?

Best regards,

Charlie

1. Yes; Akira's code first preallocates an array of NaN of the size of the maximum length of the input files in case they're not all the same. This loop just fills the non-empty rows of each column with the array of the specific file--since it's writing into a pre-existing array, must use explicit addressing -- writing just tData(:,kk)=... would require there to be the same number of rows in each file; writing tData=... would not error syntactically, but would overwrite the entire array variable with the content of each in turn, leaving only the last as a one-column variable. It's always good to write general code but if you have a specific case where you know all the files are the same length, then you could shortcut the operation and remove a little of the logic. I didn't look at the files, but if there is only one time column for all, I'd presume then they do all match up; otherwise it would seem you would need to have a separate timestamp for each.

2. The '@' is the syntax to tell MATLAB interpreter it is a function handle, not to try to execute the function. The function to execute on the cell content is what cellfun expects as the first argument.

3. I didn't download the file to look at, but almost certainly can use readtable directly and is also almost certainly what I would have done -- and then use table2timetable instead of array2timetable if you didn't already have the array in the code to pick up on. Unless the file format is really funky readtable perhaps with some help from an import options object can almost always manage to bring it in first shot as is desired. This can include cleaning up variable names, conversion to desired data types, handling missing values, etc., etc, etc., ... all at once. It may not be time effective for only a one-shot operation, but if going to process multiple files of the same type, it is generally well worth some upfront time.

Thank you dpb, much appreciated!

"I would recommend not to use white space in variable names of a table variable."

That's easily dealt with

just remove the space from "Test" string. If one is building the variable names programmatically, it really is of little consequence; if typing by hand it's a little more work to quote them, granted, and I generally don't use embedded spaces in variable names (or file names, either, for that matter) for that reason.

One can sorta' get both the visual effect and avoid needing to quote them by the expedient of the underscore, of course--

In studying this problem, I have tried and gone through the code; and also tried out the suggested

But it has yielded me the same error...I have observed the the following info should be paid attention to:

"The VariableNames property must be a cell array, with each element containing one nonempty character vector." found in the table VariableNames documentation. So the problem is solved by being able to convert the string array, Header, to a cell array of character vectors. This is achieved using the cellstr function. I have tried the following code and got the result shown below (Hope it is this that the questioner sought after)

For the first ten rows of the output table....

Samuel, you must be using a version of MATLAB from around 2016 (or something funny is going on). From sometime around 2018, the variable names need not be a cellstr.

Also a minor suggestion:do the creation and naming all on one line.

output=array2table(datapool,'VariableNames',Header)