MATLAB Answers


Function returning ans instead of three outputs

Asked by Sara Foster on 8 Sep 2019
Latest activity Edited by Stephen Cobeldick on 8 Sep 2019
My function is:
function [R,G,B] = MostDistantPixel(pixels)
%rest of code
R = ipixel(1)
G = ipixel(2)
B = ipixel(3)
On the command window it says R = 50, G = 48, and B= 47.
However, it is not returning these outputs and returning only the first output R with a value of 50. How do I fix this?


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1 Answer

Answer by Stephen Cobeldick on 8 Sep 2019
Edited by Stephen Cobeldick on 8 Sep 2019
 Accepted Answer

You need to call the function with three output arguments, e.g.:
inp = [...]; % your input array
[RR,GG,BB] = MostDistantPixel(inp)
Very basic MATLAB concepts, such as how to call functions with multiple input/output arguments, are explained in the introductory tutorials:
Note that if a function that returns an output and it is called without any outputs being allocated to a variable, then its first output will be assigned to the default variable ans:
It is recommended to avoid referring to ans in code: it is recommended to always define your own output variables.
PS: You will probably also want to suppress the displaying of R, G, and B using semi-colons.


This makes so much sense! So let’s say I use this function in another function, it will return the three outputs? Sorry, quite new to matlab.
"So let’s say I use this function in another function, it will return the three outputs?"
Where you call it from makes absolutely no difference: if you define your function with three output arguments then when you call it you can allocate those three outputs to three variables. It makes no difference if you do this from the command line, inside another function, or in a script: the syntax is always the same (just like I showed in my answer).
Note that you can also call a function with fewer outputs than the function defines, the unassigned outputs are then essentially ignored (however in some cases, e.g. meshgrid, ndgrid, find, size, etc., the number of output arguments used can also change the functionality).
Thank you! This has helped me a lot.

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