how to use value of a string variable in another function

Hi. I am trying to use union() to find union of some arrays which are belong to a cell. And I want to that in a loop. Here is what I have done so far (actually nothing), but still:

str='';
for i=1:G.NodeCount
    str=strcat(str,'cell2mat(R{',num2str(i),',1}(:,1)),');
end
str = str(1:end-1); %delete the last comma

The result of str is exactly the what I want, but I am not going to put it here due to the length. However I'd like to show first three and the last one (comma seperated):

cell2mat(R{1,1}(:,1)),cell2mat(R{2,1}(:,1)),cell2mat(R{3,1}(:,1))...cell2mat(R{129,1}(:,1))

Finally, I want to use the value of 'str' in the union() function. None of them below are worked:

result=union(disp(sprintf('%s\n',str)));
result=union(disp(str));
result=union(sprintf(str));
result=union(sprintf('%s\n',str));
result=union(fprintf(str));
result=union(fprintf('%s\n',str));

What can I do else? Thanks in advance.

[Jan]

Of course the posted commands worked, but they to not do, what you expect. You are packing code inside a string, this means that you confuse data and the program.

Please explain what the contents of R is and what you want as result. Posting code, which does not do what you want, does not allow us to guess the intention.

[Stephen23]

@Emrah: you seem to be constructing code as strings, which presumably you will try to execute. This is a very buggy, slow, and unclear way to write code. Executing strings will make your own life much harder. You might like to consider changing to use more efficient coding paradigms.

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

[Emrah]

I know that @Stephen, But I couldn't find any other solution for problem. Do you have any? If you do, please share with me. Thanks.

Answer 1

[Walter Roberson]

result = [];
for K = 1 : length(R)
  result = union(result, R{K});
end