Dynamically labelling in MATLAB - matlab

Question

I have a MATLAB script which creates an matrix, 'newmatrix', and exports it as matrix.txt:
save -ascii matrix.txt newmatrix
In my script I also calculate the distance between certain elements of the matrix, as the size of the matrix depends on a variable 'width' which I specify in the script.
width = max(newmatrix(:,5)) - min(newmatrix(:,5))
x_vector = width + 2
And the variable x_vector is defined as width + 2
I want to know is it possible to export x_vector, labelling it as, eg my_vector $x_vector so that "my_vector 7.3" will be produced when the value of x_vector is equal to 7.3
I have tried:
save -ascii 'my_vector' + x_vector
But receive the following errors:
warning: save: no such variable +
warning: no such variable 'my_vector'

Answer 1

Three things:
1) I prefer to use functional form of the calls so that you can pass in variables rather than static strings.
save -ascii matrix.txt newmatrix
is equivalent to:
save('-ascii','matrix.txt','newmatrix')
In other words, in the first form all inputs get treated as string inputs to the function.
2) You can't add character arrays in Matlab. Rather you concatenate them or use sprintf.
name = sprintf('my_vector_%g',x_vector);
save('-ascii',name)
Note by using the functional form we can now pass in a variable. Note however this won't work because name should be either a valid option or a variable, and my_vector_7.3 isn't either.
3) I'm not entirely sure what you're asking, but I think you want the text file to say "my_vector 7.3". I don't think -ascii supports strings .... You could write something using fprintf.
fid = fopen('matrix.txt','w');
fprintf(fid,mat2str(new_matrix));
fprintf(fid,'\n');
fprintf(fid,'my_vector %g',x_vector);
fclose(fid);