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How to assign default values to function inputs

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K E
K E on 30 Nov 2016
Commented: K E on 2 Dec 2016
I have a function with some required inputs,
heatContent = function(swRadiation, lwRadiation)
If the user passes in [] for any of the inputs, I would like to substitute default values (swRadiation=100 or lwRadiation=50). Also if the user only passes in 1 input, I would substitute in lwradiation=50 for the second input. I believe I can use inputparser to do this, but the following gives an error (Undefined function or variable 'lwRadiation'). I could write a long chain of if/elseif statements but suspect there is a more compact way.
p = inputparser;
addOptional(p,'swRadation',50);
addOptional(p,'lwRadiation',100);

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Accepted Answer

Jan
Jan on 30 Nov 2016
Edited: Jan on 30 Nov 2016
How should the code decide which input was given, when you provide one input only?
The inputParser is a powerful tool. But hard coding is not complicated here:
function heatContent = function(swRadiation, lwRadiation)
switch nargin
case 0
swRadiation = [];
lwRadiation = [];
case 1
lwRadiation = [];
case 2
otherwise
error('2 inputs are accepted.')
end
if isempty(swRadiation)
swRadiation = 50;
end
if isempty(lwRadiation)
lwRadiation = 100;
end
...
The inputParser expects name-value pairs to identify the inputs. This allows to change the order of the inputs and you can provide the 2nd input only without ambiguities.

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K E
K E on 2 Dec 2016
It is good to know that there is not in fact a shortcut via inputparser, and that if statements are a fine approach.

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