Rename workspace variable (table) with a string value within a loop

Hello, I am trying to process some data and want to upload all the files from a specific experiment over time.

tank=['02'] % insert experiment number
days=[21:25]; % insert date range
for d=1:length(days)
    filename = ['201708' num2str(days(d)) '_tank' tank '_down_01.txt'];
    T = readtable(filename);
    z=filename(7:15);
    %
    % INSERT CODE HERE THAT ALLOWS ME TO RENAME T AS THE CONTENTS OF STRING z - HELP!
    %
    clear T
end

It'd be great if someone could help with the code! I'm trying to get away from using EVAL as I know that's not good programming etiquette... Maybe assignin ?

[Jos (10584)]

Why do want to do that? It is easier to use the same variable name for all the code. I you want to store multiple data into a single variable use a struct or a cell array

DATAC{d} = T ;
DATAS(d).values = T ;

[Stephen23]

"I'm trying to get away from using EVAL as I know that's not good programming etiquette"

"Etiquette" is an interesting descriptor for the fact that using eval to magically access variables makes your code slow, complex, buggy, insecure, hard to debug, and obfuscates the code intent.

https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval

This has been discussed a thousand times before, and each of those discussions explains better alternatives: just use indexing or fieldnames.

"INSERT CODE HERE THAT ALLOWS ME TO RENAME T AS THE CONTENTS OF STRING z - HELP!"

That is exactly what you should not do. The problem is not eval in itself as you seem to think, the problem is caused by magically creating or accessing variable names dynamically. Read these to know more:

https://www.mathworks.com/matlabcentral/answers/364851-assignin-and-eval-functions

https://www.mathworks.com/matlabcentral/answers/352237-is-there-the-more-elegant-way-to-do-this

[Matt J]

I'm trying to get away from using EVAL as I know that's not good programming etiquette... Maybe assignin

Assignin has the same hazards as eval. The same for evalin() and load() ... basically anything capable of implicitly creating variables in the workspace.

Answer 1

[Matt J]

If strings really are the most convenient way to differentiate the tables, then I would use dynamic structure field names.

S.(z)=T;

Functionally, there is no difference between a variable and a structure field, except that the latter can be dynamically named, gracefully.

Answer 2

[Stephen23]

Note that the data being encoded is fundamentally numeric (days and experiment number). Rather than awkwardly and pointlessly converting numeric data to string you can just use a simple non-scalar structure to hold your data:

https://www.mathworks.com/help/matlab/matlab_prog/access-multiple-elements-of-a-nonscalar-struct-array.html

Exactly as Jos (10584) wrote twelve hours ago:

DATAS(d).values = T ;

Answer 3

[Russell Arnott]

Thanks for your suggestions every one :-)