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Tilde doesn't work for ignoring my inputs

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I have a function
function [output] = myfunction(a,b,c)
Which can run without any inputs because I coded "default" inputs using if ~exist. I.e. I can type myfunction in the command box and it will run.
However, when I try myfunction(~,~,c) for instance, it says that "Using ~ to ignore a value is not permitted in this context."
Any ideas?
Thanks.
PS: I know about vargin. I'd rather avoid it if possible.

Accepted Answer

Steven Lord
Steven Lord on 6 Jun 2016
You can use tilde to ignore input arguments when you define the function.
You cannot use tilde to ignore input arguments when you call the function.
You cannot use tilde to ignore output arguments when you define the function.
You can use tilde to ignore output arguments when you call the function.
If you want to be able to specify only the third argument, there must be some way for your function to disambiguate the one-input call from a call that specifies only the third input. Usually in MathWorks function this is done by specifying [] for the arguments for which the user doesn't want to specify. In that case the code would use the default value if either nargin is too small or if nargin is large enough and the specified input argument isempty.
  9 Comments
Jessica Avellaneda
Jessica Avellaneda on 27 Sep 2020
What can I use to ignore inputs arguments when I call the function?
Walter Roberson
Walter Roberson on 27 Sep 2020
You cannot ignore input arguments when you all the function.
If the function itself is ignoring that argument, then you can pass anything of any datatype, but you have to pass something (even if empty)
If the function itself is not ignoring that argument, then it needs to receive something (unless it is a trailing argument and the function is using nargin to detect whether trailing arguments were passed in). The convention for Mathworks functions is that [] is passed to hold a place to permit a later meaningful argument to be passed.

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