How to loop through a series of variables, named with strings but including numbers? -Undefined function or variable

Hi, I'm an undergraduate researcher trying to figure out how to generate values from a bunch of different datasets. I have 12 matrices from 12 different files, each of which has two fields. The fields in different matrices are the same except for a number tagged onto the end. So the first matrix has fields a_1 and b_1, the second has fields a_2 and b_2, the third has fields a_3 and b_3, etc. I want to multiply the first field of each matrix by the second field of the same matrix and sum it, and I'd like to do this in a loop. Right now I have this:

for i = 1:12; x_i = sum(a_i'*b_i'); A{i} = [i; x_i]; end

I'm trying to get a final matrix A with the numbers 1:12 as field one and the corresponding x value in field 2.

I have very little experience with loops in matlab. Thanks so much for your help!

[KSSV]

What you are trying is allocating a dynamic naming of variables which is not at all suggested and required. You have the matrices in file, you can straight a way read them into 3D matrix and do what you want.

[Stephen23]

@Niky Taylor: can you please upload a sample file by making a new comment and clicking the paperclip button. Most likely the best solution would be to import that data into one array, such as an ND array or perhaps a non-scalar structure.

You write that "So the first matrix has fields a_1 and b_1": is the matrix a structure (only structures have fields), or is the matrix numeric type? You write that "12 matrices from 12 different files": are these .mat files, or some other file format?

If you upload your data then we can see exactly what you are trying to explain.

Answer 1

[Walter Roberson]

http://matlab.wikia.com/wiki/FAQ#How_can_I_create_variables_A1.2C_A2.2C....2CA10_in_a_loop.3F

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