Help with commands varargin and switch

[EDIT: Mon May 16 20:51:23 UTC 2011 - Reformat - MKF]

Hello,

I am new to MATLAB and I am trying to understand the code given in the following paper (Matov et al 'Analysis of microtubule dynamic instability using a plus-end growth marker', Nature, 7, 761-768 (2010).

One of the codes uses command varargin and switch. Could someone please explain the use of these command in MATLAB.

Part of the code is given below %START

function [cutoffIndex, cutoffValue, sp, axesH] = cutFirstHistMode(varargin)

% goodDataIdx is used in case data contains nans

goodDataIdx = [];

% check for axesHandle

if ishandle(varargin{1})

    axesH = varargin{1};
    varargin(1) = [];
    verbose = 1;

else

    axesH = [];

end

switch length(varargin) - isscalar(varargin{end})

    case 1 % data
        doHistogram = 1;
        data = varargin{1};
        data = data(:);

%END. I have given only a part of this code.

Your help is truly appreciated.

Thanks.

Answer 1

[Matt Fig]

Probably the best thing is for you to read the doc on these topics.

VARARGIN

SWITCH

[NS]

Thanks Matt.

So does varargin include all the inputs in your function? If this is the case varargin{1} will be the first and varargin{end} is the last. Am I correct?

Also, could you explain 'if ishandle(varargin{1})' in the code. I always assumed the if operator to have a proportionality sign like "< > =" etc.

Thanks.

[Jan]

IF needs a logical expression as argument. The relational operators like ">" or "==" (not "=" !) reply a logical value, e.g. "2 > 3" replies FALSE. The function ISHANDLE replies a logical value also.

You can simply try what VARARGIN does: Let Matlab explain it itself by doing.

[NS]

Thanks Jan.

I ran the code. The "if" operator processed the true statements if the argument had a positive value (not 0).

eg. when ishandle(varargin{1})=1 the if statement was processed and when the value was 0 the else statements were processed.

Also I understood what varargin stands for after running the code. Thanks once again

[Jan]

Be careful: "ishandle(varargin{1})=1" is not a comparison, but a standard bug. You want: "ishandle(varargin{1})==1". "if ishandle(varargin{1})" works also, because ISHANDLE replies a LOGICAL already.

"if X" with a numerical X (even an array!) means explicitely: "if all(X) && ~isempty(X)".