iFit/fix

 b = fix(s, parameters, ...) : sets parameter lock (fix) for further fit using the model 's'

   @iFunc/mlock lock model parameters during further fit process.
     to lock/fix a parameter model, use fix(model, parameter)

   To lock/fix a set of parameters, you may use a regular expression as:
     fix(model, regexp(model.Parameters, 'token1|token2|...'))

   fix(model, {'Parameter1', 'Parameter2', ...})
     lock/fix parameter for further fits
   fix(model)
     display fixed parameters
   fix(model,'all')
     fix/lock all parameters
   fix(model,'none')
     free/unlock all parameters

 input:  s: object or array (iFunc)
         parameters: names or index of parameters to lock/fix (char or scalar)
 output: b: object or array (iFunc)
 ex:     b=fix(a,'Intensity');

 Version: Aug. 22, 2017
 See also iFunc, iFunc/fits, iFunc/munlock, iFunc/xlim