# How to add the strings in three for loops

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what I want is to add 9terms(all k & m) for each i(1:3). h_1, h_2, h_3 each will have 9 additive terms. Example, h_1= h_1_1_1*a_1*b_1+ h_1_1_2*a_1*b_2+.......+h_1_3_3*a_3*b_3.
ht=cell(3);
for i=1:3
for k=1:3
for m=1:3
code2=['h_',num2str(i),'=h_',num2str(i),'_',num2str(k),'_',num2str(m),'*a_',num2str(k),'*b_',num2str(m)];
ht{i}=strcat(ht,'+',code2)
eval(ht(i));
end
end
disp(ht(i));
end
Stephen23 on 11 Sep 2018
Indexing would be much simpler and much more efficient.
The MATLAB documentation specifically warns against going exactly what you are trying to do: "A frequent use of the eval function is to create sets of variables such as A1, A2, ..., An, but this approach does not use the array processing power of MATLAB and is not recommended. The preferred method is to store related data in a single array."
Magically accessing variable names is one way that beginners force themselves into writing slow, complex, buggy code that is hard to debug:

Naman Chaturvedi on 11 Sep 2018
Correct code:
ht=cell(3,1);
for i=1:3
for k=1:3
for m=1:3
if (k*m==1)
code2=['h_',num2str(i),'=h_',num2str(i),'_',num2str(k),'_',num2str(m),'*a_',num2str(k),'*b_',num2str(m)];
ht{i}=[ht{i},code2];
else
code2=['h_',num2str(i),'_',num2str(k),'_',num2str(m),'*a_',num2str(k),'*b_',num2str(m)];
ht{i}=[ht{i},'+',code2];
end
end
end
disp(ht(i));
end
Mahmuda Ishrat Malek on 14 Sep 2018
Can you give a short example on how I can do this sort of thing with indexing?