How can I use a for loop to reassign matrix names?

Hi there! I am trying to write a 'for' loop which does the following:

for i = 1:9
    a = a0i; b = b0i; cx = c0i(:, 1); cy = c0i(:, 2); t = t00i;
    foneplotp(a, b, cx, cy, t, period)
end

I have matrices labeled a01, a02, a03, etc. in my workspace, but when I try to run this, I get the error:

Undefined function or variable 'a0i'.

Is there a way to do this with a 'for' loop in MATLAB?

Thanks!

Miranda

Answer 1

[Star Strider]

It’s horrible programming style, but it’s possible. So long as your matrices already exist and you simply need to call them, here is an example of what you can do:

a01 = pi;
c01 = [5 7];
for i = 1:9
    a  = eval(sprintf('a0%d',i))
    cx = eval(sprintf('c0%d(:, 1)',i))
end

I used a01 and c01 to test the code, so remove those in your actual code. I listed them here so you can test them to see how it works.

[Miranda]

Thank you so much! Even if it is horrible programming, it's only for data analysis.

[Star Strider]

My pleasure!

The sincerest expression of appreciation here on MATLAB Answers is to accept the answer that solves your problem. It also helps others with similar questions find them.

Answer 2

[Image Analyst]

Why complicate it? Just do

foneplotp(a01, b01, c01(:,1), c01(:,2), t001, period);
foneplotp(a02, b02, c02(:,1), c02(:,2), t002, period);
foneplotp(a03, b03, c03(:,1), c03(:,2), t003, period);
foneplotp(a04, b04, c04(:,1), c04(:,2), t004, period);
foneplotp(a05, b05, c05(:,1), c05(:,2), t005, period);
foneplotp(a06, b06, c06(:,1), c06(:,2), t006, period);
foneplotp(a07, b07, c07(:,1), c07(:,2), t007, period);
foneplotp(a08, b08, c08(:,1), c08(:,2), t008, period);
foneplotp(a09, b09, c09(:,1), c09(:,2), t009, period);

It's only 9 lines long and a heck of a lot simpler to understand and maintain than the crazy workaround mentioned in the FAQ

[Miranda]

That would be okay, but in reality, I have a varying number of these matrices. In some runs, I have up to 100, while in others I only have 10 or 25. I don't want to hardcode it for every data set.

[Image Analyst]

You should NOT have 100 differently named variables! How did you ever create those in the first place? Did you use the method that the FAQ shows you but advises against ? Well you can do the same thing to get those names and assign them to other variables like a,b,c, etc.

You should use a 2D array instead of different names. This is what the FAQ strongly recommends . Please don't do what you are asking.

[Miranda]

My main programming is in FORTRAN and it prints out to a MATLAB-readable file. It's not the cleanest way to program, I know. The issue is that I am printing out several hundred lines of data at each time step (which refers to the 01, 02, 03, etc.) which correspond to several hundred different calculations.