vlt.neuro.vision.contrast.indexes.contrastfit2sensitivity

  CONTRASTFIT2SENSITIVITY - Compute contrast sensitivity

   [S,C_CRITERON] = vlt.neuro.vision.contrast.indexes.contrastfit2sensitivity(...
    NKPARAMETERS, CRITERION)

   Given Naka-Rushton fit parameters (either [Rm C50], [Rm C50 N], or [Rm C50 N S])
   computes the first contrast C_CRITERION where the response exceeds CRITERION.
   The sensitivity S = 1/C_CRITERION is also computed.

   If there is no response that exceeds the criterion, then the sensitivity S is 0
   and the C_CRITERION is Inf.

   Example:
     c = 0:0.1:1;
     rm = 10;
     c50 = 0.3;
     r = rm*vlt.fit.naka_rushton_func(c,c50);
     figure;
     plot(c,r,'b-');
     xlabel('Contrast'); ylabel('Response'); box off;
     [s,c_criterion] = vlt.neuro.vision.contrast.indexes.contrastfit2sensitivity([rm c50],2);
     hold on
     A = axis;
     plot(c_criterion*[1 1],A([3 4]),'k-');
     title(['Contrast sensitivity is ' num2str(s) '.']);