function doesnt works well

Hi, I am using this function;

function [s,tint] = spei(t,prec,pevap,varargin)

But, I am not sure what is varargin works for?

The size of my file are;

t=1x1x420

prec=98x56x420

pevap=98x56x420

Error using spei (line 40)

Expected a string scalar or character vector for the parameter name.

[Star Strider]

It will be necessary to carefully read the documentation for the file to understand what the arguments must be, and what their order must be.

[Rik]

Function posted in duplicate question:

function [spei_index]=calculate_spei(t,prec,pevap,varargin);
[nlon, nlat, n]=size(prec);
prec=squeeze(prec);
for i=1:nlon
    for j=1:nlat
        if isnan(prec(i,j,1))==0
            spei_index(i,j,:)=spei(t,prec(i,j,:),pevap(i,j,:),varargin);
        else
            spei_index(i,j,:)=ones(1,n-12)*NaN;
        end
    end
end

Answer 1

[Walter Roberson]

spei_index(i,j,:) = spei(t, prec(i,j,:), pevap(i,j,:), varargin{:} );

is my guess.

[Rik]

Good catch, I should have spotted this. I'll leave my answer up for documentary purposes.

[Nurul Ain Basirah Zakaria]

I can use this function on vector,

s = spei(t',prec,pevap);

prec=420x1

pevap=420x1

but, i need to do a loop for a prec=58x69x420 right?

[Walter Roberson]

No, that is not needed. The documentation states

% s = spei(t,prec,pevap) computes the standardised precipitation-evapotranspiration
% index s, given precipitation prec and potential evaporation pevap corresponding 
% to times t. prec and pevap can be either be 1D vectors or 3D cubes, whose
% first two dimensions are spatial and whose third dimension corresponds to times 
% t. The dimensions of prec and pevap must agree. Times t can be datetime 
% or datenum format. 

so passing in a vector of times of length 420 is fine if your prec and pevap are something by something by 420.

[Nurul Ain Basirah Zakaria]

so it should be okay right if my data:

prec=98x56x420

pevap=98x56x420

and

t=1x420

[Nurul Ain Basirah Zakaria]

but, this is my error

Error using rect2cube (line 46)

Error: Dimensions of the gridsize must match the number of columns in A2.

Error in spei (line 117)

s = rect2cube(s,gridsize);

Answer 2

[Rik]

varargin is typically used to capture optional input arguments:

help varargin

 VARARGIN Variable length input argument list.
    Allows any number of arguments to a function.  The variable
    VARARGIN is a cell array containing the optional arguments to the
    function.  VARARGIN must be declared as the last input argument
    and collects all the inputs from that point onwards. In the
    declaration, VARARGIN must be lowercase (i.e., varargin).
 
    For example, the function,
 
        function myplot(x,varargin)
        plot(x,varargin{:})
 
    collects all the inputs starting with the second input into the 
    variable "varargin".  MYPLOT uses the comma-separated list syntax
    varargin{:} to pass the optional parameters to plot.  The call,
 
        myplot(sin(0:.1:1),'color',[.5 .7 .3],'linestyle',':')
 
    results in varargin being a 1-by-4 cell array containing the
    values 'color', [.5 .7 .3], 'linestyle', and ':'.  
 
    See also VARARGOUT, NARGIN, NARGOUT, INPUTNAME, FUNCTION, LISTS, PAREN.

    Documentation for varargin
       doc varargin

Since you don't use the optional/unnamed inputs, there shouldn't be any issues.

The function you're using should have documentation explaining how to use it. Read it. If you don't understand it, please provide a reference to where you got this function (as I can't find it).

[Nurul Ain Basirah Zakaria]

I got the function from here.

I don't really understand it.

[Walter Roberson]

In that case my suggestion was correct.