Build Matrix from Text file or String

Hey Guys, I'm working with Mathematica and MatLab and I just wrote a function, which translates the results (matrices and vectors) I get in Mathematica (saved as a .txt-file) into the syntax I'm using in my MatLab script. The output of this function is a char-array and I also save it as a .txt-file. Which looks like that:

'[1 2 3;4 5 6;7 8 9];'

And I want to have this as an actual asignment for the matrix-elements, so something like that:

A=[1 2 3;4 5 6;7 8 9];

Is there a way to convert this character array into an actual MatLab command to asign the matrix-elements?

[Stephen23]

"I just wrote a function, which translates the results (matrices and vectors) I get in Mathematica (saved as a .txt-file) into the syntax I'm using in my MatLab script"

Trying to evaluate that string will be waste of your time and MATLAB's time. You would be much better off writing the data to a standard CSV file, so it looks like this:

1,2,3
4,5,6
7,8,9

And then simply importing that into MATLAB using csvread:

A = csvread(...);

Using any of the standard file input-output formats and functions will be a lot simpler, waste less time, and be more efficient than what you are trying to do.

[Jakob]

Thanks a lot, yeah that sound way easier! But this was just an example, the matrices are way more complex containing functions for the matrix-entries. Does that still work with entries like e.g.:

-l2(1)*(G(2,5)*sin(t(1)-t(3))

[Stephen23]

@Jakob: you are trying to use MATLAB as a parser, which is rarely efficient. It may be simpler to create those files to contain valid MATLAB code, and then just call the script.

[Jakob]

Thanks Stephen, but I don't really understand what you mean. Just to explain, why I need this... I have to calculate the matrix entries new in each iteration, and the matrix entries should be the description for the calculation. So can I use characters in the CSV-file? The equations will then probably be handeled like strings.

Answer 1

[KSSV]

A = '[1 2 3;4 5 6;7 8 9];'
B = str2num(A)

[Stephen23]

This works, but is very inefficient and relies on eval. The best solution would be to import that data properly by writing a standard file format and import that as numeric data.