Functions with a flexible list of ordered/unordered and labeled/unlabeled inputs in MATLAB

Question

A lot of MATLAB functions have an input structure such as:

output = function MyFun(a,b,c,\'-setting1\',s1,\'-setting2\',s2,\'-setting3\',s3)

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Answer 1

The InputParser class addresses all of these issues. You can specify any number of:

1. Required parameters (ordered, unlabeled)
2. Optional parameters (ordered, unlabeled)
3. String parameter-value pairs in any order (unordered, labeled)

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A very clear tutorial with examples is provided by MathWorks. For a function defined as function printPhoto(filename,varargin), the example boils down to the following.

Create the inputParser:

p = inputParser;

Specify defaults and define validation criteria:

defaultFinish = 'glossy';
validFinishes = {'glossy','matte'};
checkFinish = @(x) any(validatestring(x,validFinishes));

defaultColor = 'RGB';
validColors = {'RGB','CMYK'};
checkColor = @(x) any(validatestring(x,validColors));

defaultWidth = 6;
defaultHeight = 4;

Define required/optional/parameter input names, set their default values and validation functions:

addRequired(p,'filename',@ischar);
addOptional(p,'finish',defaultFinish,checkFinish);
addOptional(p,'color',defaultColor,checkColor);
addParameter(p,'width',defaultWidth,@isnumeric);
addParameter(p,'height',defaultHeight,@isnumeric);

Parse the inputs into a struct:

parse(p,filename,varargin{:});

Then you have the input arguments and their values in p.Results.

The InputParser class is used throughout newer MathWorks functions, so don't be afraid to use it yourself!