Ignoring an output from a Matlab function

Question

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How to elegantly ignore some return values of a MATLAB function?

I have a Matlab function with two outputs. Sometimes I use both outputs.

function [output1 output2] = myFunction(input)
[a b] = myFunction(input);

Other times I only need output1 and don't want to waste memory assigning output2

a = myFunction(input);

However, I can't figure out a simple way to give the reverse scenario (only need output2 and don't want to waste memory assigning output1). I thought it would be something like

[~ b] = myFunction(input)

but that doesn't seem to work. Anybody have suggestions for a quick solution? Thanks for your help!

you are missing a comma: `[~,b] = myFunction(input)` – Amro Jul 05 '11 at 19:09 — Amro, Jul 05 '11 at 19:09

score 2 · Answer 1 · answered Jul 05 '11 at 19:09

2

It's [~, b], not [~ b]. The comma is missing.

answered Jul 05 '11 at 19:09

Phonon

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I get the following error when I add the comma: Error: Expression or statement is incorrect--possibly unbalanced (, {, or [. – yy08 Jul 05 '11 at 19:11
What does your call look like? Post the actual line you use to call it. – Phonon Jul 05 '11 at 19:12
2

@yy08: `~` was only introduced in MATLAB R2009b, what version are you working with? – Amro Jul 05 '11 at 19:16
'[~, b] = myFunction(input)'. I'm using version 2007b so that might explain it. – yy08 Jul 05 '11 at 20:19
Tried it on a computer with 2010b. Works fine. Thanks for the help! – yy08 Jul 05 '11 at 20:35

score 0 · Answer 2 · answered Jul 05 '11 at 19:06

the object will be created inside myFunction either way, unless your input has a way to prevent the creation. If you can prevent the creation internally, you can modify myFunction to return a cell array or other structure, from which you can decide which elements to keep. If your concern is that [dontwant b] is wasting matlab memory by holding dontwant, then you might want to delete dontwant from your workspace by calling

clear dontwant;

Ignoring an output from a Matlab function

2 Answers2