Matrix dimensions must agree

Hello!

I have written the code which uses a function

function f1=F_1(y,z);

global gamma

global a

f1=-(1/2)*exp(-(z-a)./(1+gamma*cos(2*pi*y)))+1/2;

end

When I try to run I get a error Error using / Matrix dimensions must agree

Could you please help me?

Thank you in advance.

Elena

Answer 1

[the cyclist]

Guessing you need .* rather than just * after gamma.

If that does not fix it, can you please specify what the sizes of your variables a,gamma,y,z are?

[Elena]

Thank you very much. and sorry I'm very new in Matlab

[Image Analyst]

If that was the correct answer, then gamma MUST have been an array. If so, then your code is not very robust. For example, you don't have a try/catch. What guarantees that gamma has the same number of elements as y? Are you checking for that before you call this function? A robust function would check for that inside itself rather than assume. Even if it did assume, it should have a try/catch just in case, so that you can inform your user of some error. Better would be if you passed in gamma and a rather than make them global, but I know that if gamma and a were not available in the calling routine that it might be more convenient to make them global rather than passing them down through a bunch of nested functions that don't use them. Try using code such as this

function f1=F_1(y,z) % Note: I did not use a semi colon like you did.

global gamma

global a

f1 = []; % Initialize - needed in case of error.

try

lz = length(z);

lg = length(gamma);

ly = length(y);

if lz ~= ly || lg ~= ly

errorMessage = sprintf('Dimensions do not match.\nz had %d elements.\ngamma has %n elements.\ny has %d elements', lz, lg, ly);

uiwait(warndlg(errorMessage));

return;

end

% If we get to here, the dimensions match.

f1=-(1/2)*exp(-(z-a)./(1+gamma.*cos(2*pi*y)))+1/2;

catch ME

% Some other kind of error.

errorMessage = sprintf('Error in function F_1.\n\nError Message:\n%s', ME.message);

fprintf(1,'%s\n', errorMessage);

uiwait(warndlg(errorMessage));

end

Answer 2

[Image Analyst]

You should really learn how to use the debugger. It's much more efficient than asking us for every simple thing like this. For example, if you put a breakpoint at that line and examine the lengths of y,z, gamma, and a, you'll probably find that some of them aren't scalars and those that aren't don't have the same lengths.

[the cyclist]

+1 to this advice