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inputparser mistakes option for value

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Hello, I have created a method to draw some plots.
I have used inputParser to assign optional parameters (e.g. the y-axis label or the legend).
Here is the code:
function plot1signal(signal,titleName,varargin)
% Function to plot one signal per figure
% defaults
default_legendName = '';
default_yLabel = 'default';
p = inputParser;
validSignal = @(x) (isa(x,'timeseries') || isstruct(x));
addRequired(p,'signal',validSignal);
addRequired(p,'titleName',@ischar);
addOptional(p,'legendName',default_legendName,@ischar);
addOptional(p,'yLabel',default_yLabel,@ischar);
parse(p,signal,titleName,varargin{:});
...
end
As you can see there are 2 required inputs (a signal and the title), and two optional (y-label and the legend string).
I call this function with:
plot1signal(the_signal,'Title','yLabel','kN')
The expected behavior of the method would be having the default value for legendName and 'kN' for yLabel. Unfortunately inputParser seems to intepret 'yLabel' not only as an option but also as the input for 'legendName':
p.Results
ans =
struct with fields:
legendName: 'yLabel'
signal: [1×1 struct]
titleName: 'Title'
yLabel: 'kN'
Am I missing something?
  1 Comment
Athrey Ranjith Krishnanunni
addOptional adds optional positional arguments to your function, not Name-Value pairs. So, when you call your function as
plot1signal(the_signal,'Title','yLabel','kN')
inputParser takes the 1st and 2nd optional arguments as the values for legendName and yLabel, respectively (because they are positional, and you added legendName first to your function, followed by yLabel).
What you probably need is
addParameter(p,'legendName',default_legendName,@ischar);
addParameter(p,'yLabel',default_yLabel,@ischar);
instead.

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Accepted Answer

Prudhvi Peddagoni
Prudhvi Peddagoni on 19 Jan 2021
Hi,
Adding to what ARK has said, You can see the difference between functions like addRequired , addOptional and addParameter in this example.
Hope this helps.

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