Matrix dimensions must agree.

This function make a coordinates from sensor in another coordintes and scale from mm to m. but it gives me the following error message (Matrix dimensions must agree.) at line: Bix = Bix .* sign(MP).* 1000;

    % code
MP = [P0(:,3), P0(:,4), P0(:,5)] ./ 1000; 
Bix = [(interp3 (xs, ys, zs, Bxs, abs(MP(:,1)), abs(MP(:,2)), abs(MP(:,3))));...
       (interp3 (xs, ys, zs, Bys, abs(MP(:,1)), abs(MP(:,2)), abs(MP(:,3))));...
       (interp3 (xs, ys, zs, Bzs, abs(MP(:,1)), abs(MP(:,2)), abs(MP(:,3))))];
Bix = Bix .* sign(MP).* 1000; 
Bix = Bix .* [1, -1, -1];

[José-Luis]

Have you tried using the debugger and looking at the size of the offending variables?

Are you trying to to implicit expansion for arithmetic operations and your Matlab < R2016b?

[KSSV]

Sizes of Bix and sign(MP) should be same.....They are not in your case.

[José-Luis]

They don't need to be the same if OP is trying to do implicit expansion.

[KSSV]

@Jose-Luis..Run this

K = rand(1,10).*rand(1,5)

[José-Luis]

You're not getting my point, I think.

https://blogs.mathworks.com/loren/2016/11/10/more_thoughts_about_implicit_expansion/

Arrays no longer need to have the same number of elements for such arithmetic operations to produce results.

Unsolicited disclaimer: I am having a hard time liking that. I'll eventually get on with the times.

Answer 1

[Jan]

Use the debugger to identify the problem. Set a breakpoint in the failing line:

Bix = Bix .* sign(MP).* 1000;

Then run the code again until it stops. Not check the dimensions:

size(Bix)
size(MP)

For a proper elementwise multiplication, the dimensions must match. Do they?

Note that Matlab >= 2016b can auto-expand dimensions. With older versions, bsxfun helps. Perhaps you want:

Bix = bsxfun(@times, Bix, sign(MP)) * 1000;

Maybe a reshape helps here to adjust the dimensions as wanted.