Replace the variable with it's contents to access a struct

I have a list of 20+ struct that i want to do some math on. Since i need to to similar math to several of the structs i want to automate it as much as possible.

The structs are named Axxxx so i made a for loop where i create value in the variable that is the name of the struct. How do i then use whats in the variable with the struct.

First = 'A00';

for k = 1 : 21

A_temp = append(First,num2str(k-1));

A_temp.new_column = A_temp.old_column/15; <--- This does not work, but might display what i want to do.

end

A_temp now contains say 'A0020' as a string, how do i access that struct using the variable A_temp containing 'A0020'

A_temp.kanal1 becomes A0020.kanal1

I hope my question is understandable

Kind Regards

David

[Matt J]

TUTORIAL: Why Variables Should Not Be Named Dynamically (eval)

[Stephen23]

"The structs are named Axxxx ..."

And that is the start of your problems, right there.

"Since i need to to similar math to several of the structs i want to automate it as much as possible."

And so you designed your data to make that automation easier, e.g. by creating one cell/structure array which can be trivially accessed using basic, neat, very efficient indexing. Or did you skip that important step?

"...so i made a for loop where i create value in the variable that is the name of the struct. How do i then use whats in the variable with the struct."

Aaaahh, unfortunately that bad data design forces you into writing slow, complex, inefficient, insecure, obfuscated, buggy code which is difficult to debug:

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

Accessing your data would be trivial and very efficient with better data design e.g. using one structure array would let you use indexing. So far you have not told us the most important information: how did you get those tables into the workspace? The place where they are created in the workspace is the correct place to fix your code, e.g. by LOADing into an output variable instead of LOADing directly into the workspace.

[David Oestlund]

Ok, i think i understand.

The data comes from an assignment. There is a file when runned it will create 25 structs from some files.

So it is what it is and i will do the assingment instead of putting time in to this. Since the problem is in the creators end i will take that as it was intended.

Thank you very much for your time

Answer 1

[Vishesh]

• You can do it by saving all the variables present in the workspace in a table first and then perform your operation in the table.
• Here i am taking "A001" and "A002" as an example.
• You can optimize some of the lines of code by yourself.

clear;
A001=struct('a',2,'b',10);
A002=struct('a','4','b',20);

save('var.mat');
clear;
Tab=struct2table(load('var.mat'),'AsArray',true);


First = 'A00';
var_name=Tab.Properties.VariableNames;
var_names=[];
for i=1:length(var_name)
var_names=[var_names ;var_name{i}];
end

for k = 1 : 21
    A_temp = append(First,num2str(k-1));
    for i=1:length(var_names(:,1))
        if(strcmp(var_names(i,:),A_temp))
             Tab.(i).a=Tab.(i).a/2;
             Tab.(i).b=Tab.(i).b/5;
        end
    end
    
end

clear A_temp First i k var_names var_name

table2struct(Tab)

ans = struct with fields:
    A001: [1×1 struct]
    A002: [1×1 struct]