How to use fittype to create a new type of fit?

i am trying create a seiple fit with fittype function and i have tried many ways and i keep getting the some error:

    Error using fittype>iCreateFromLibrary (line 408)
    Library function seiple not found.

    Error in fittype>iCreateFittype (line 339)
        obj = iCreateFromLibrary( obj, varargin{:} );
  ...

My Code is the following and i kept the several ways i've already tried in comment:

%seiple=fittype('A.*exp(-exp(-(x-x0)./w)-((x-x0)./w)+1)','coefficients', {'A', 'w', 'x0'});
%seiple=fittype(@(A, w, x0, x) A.*exp(-exp(-(x-x0)./w)-((x-x0)./w)+1));
seiple=fittype('A.*exp(-exp(-(x-x0)./w)-((x-x0)./w)+1)',...
    'dependent',{'y'},'independent',{'x'},...
'coefficients',{'A','w','x0'});

seiplefit = fit(X, Y, 'seiple');

please, i appreciate any help or suggestions to make it work...

Answer 1

[Walter Roberson]

Do not pass in the name of the fittype object, pass in the object.

seiplefit = fit(X, Y, seiple);