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Can MATLAB recognized the name of a variable with input function?

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Ana D Chavez Gonzalez
Ana D Chavez Gonzalez on 15 Sep 2021
Edited: Stephen on 15 Sep 2021
I haven't tried yet, but what I want to do is ask the user for an input. For example,
x = input('what is the name of the object?')
The user will only be able to input a certain name of objects. Let's say the user chose milk and in the code milk is as follows:
milk = 30;
Can MATLAB display 30?
Thank you in advance
  1 Comment
Stephen
Stephen on 15 Sep 2021
"Can MATLAB display 30?"
Yes, but your approach forces you into writing slow, complex, inefficient, obfuscated code which is difficult to debug. Here are two much better approaches, first is to use the fields of a structure (or you can do much the same with a table):
S.beer = [1,2,3];
S.milk = [4,5,6];
x = 'milk'; % user input
S.(x)
ans = 1×3
4 5 6
Second is to simply and very efficiently store the names as data in their own right (which of course as meta-data they are) and then use basic MATLAB indexing:
M = [1,2,3;4,5,6];
C = ["beer","milk"];
M(strcmpi(x,C),:)
ans = 1×3
4 5 6
Understanding that meta-data is data is an important step to writing better code.
Avoiding INPUT means that you can write testable, expandable, callable code.

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Accepted Answer

Chunru
Chunru on 15 Sep 2021
It's possible but it should be avoided if possible.
milk = 30;
%x = input('what is the name of the object? ', 's') % use this in your program
x = 'milk'; % for the on-line version
if exist(x, 'var')
eval(x);
else
fprintf('The variable %s does not exist\n', x);
end
milk = 30

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