calling a function: "undefined function or variable 'abc'"

Hi there,

I'm trying to write my very first function and it looks like this:

function noiseSignal = add_white_noise(t_spalte, recSignal)
noiseSignal = recSignal + 1/64*randn(size(t_spalte));
end

I call the function with name and input via the command line and I get the noise on my original signal, but not under the variable "noiseSignal". I can use it via ans, but that's it. How can I save the noisy signal under "noiseSignal" for further usage?

Thanks a lot!

Answer 1

[Stephen23]

You are getting confused by the variable names that you have used inside the function. These are irrelevant. It does not matter at all what names variables have inside the function, because inside the function is a different workspace to where you are calling it. You specify the name of the output variable when the function is called. For example:

 function ns = add_white_noise(t_spalte, recSignal)
 ns = recSignal + 1/64*randn(size(t_spalte));
 end

can be called like this:

 >> noiseSignal = add_white_noise(4,[1,2,3,4])
 noiseSignal =
    0.98118   1.98118   2.98118   3.98118

You might like to read this:

https://www.mathworks.com/help/matlab/matlab_prog/share-data-between-workspaces.html

And note that how to call functions is also covered in the introductory tutorials, which are highly recommended for all beginners:

https://www.mathworks.com/help/matlab/getting-started-with-matlab.html

[Thorsten Zwinger]

Ah, that was it! Thanks a lot! I didn't know I have to call it like this:

 >> noiseSignal = add_white_noise(t_spalte,recSignal);

Up till now, I wrote only

 >> add_white_noise(t_spalte,recSignal);

Okay, I will look over the introductions. :)

[Niels]

can you see now the difference in out typing?

Answer 2

[Niels]

Hi,

if you type

a = add_white_noise(Argument1, Argument2)

the output will be saved within the variable named a. i guess you want its name to be noiseSignal, so type

% Argument1=t_spalte;
% Argument2=recSignal;
noiseSignal = add_white_noise(Argument1, Argument2)

[Thorsten Zwinger]

Yes, I thought so too and did that. (correct me if I'm wrong, but I don't see any differences between your typing and mine)

The problem is: Matlab won't save the output in the variable, only under ans.

[Stephen23]

@Thorsten Zwinger: please show us exactly how you are calling this function. Please make a comment and copy-and-paste the code that you use for calling this function.