f = 

     General model:
     f(x) = a+b*(1./(1+exp(-d*(x-c))))
     Coefficients (with 95% confidence bounds):
       a =      -6.202  (-6.372, -6.032)
       b =       4.225  (3.683, 4.768)
       c =      -1.471  (-1.587, -1.354)
       d =       3.888  (2.506, 5.27)

fgof = 

  struct with fields:

           sse: 9.5656e+03
       rsquare: 0.2291
           dfe: 1594
    adjrsquare: 0.2277
          rmse: 2.4497


fout = 

  struct with fields:

           numobs: 1598
         numparam: 4
        residuals: [1598×1 double]
         Jacobian: [1598×4 double]
         exitflag: 3
    firstorderopt: 1.3620
       iterations: 18
        funcCount: 95
     cgiterations: 0
        algorithm: 'trust-region-reflective'
         stepsize: 0.0020
          message: 'Success, but fitting stopped because change in residuals less than tolerance (TolFun).'
