sigmoid.m

可以进行曲线回归拟合算法的四参数算法。函数为 y = (a-d)/(1+(x/c)^b) +d . ec50.m 为其主要函数

function yhat=sigmoid(params4,x)
% SIGMOID Function to fit data to a four parameter dose response curve
% requires the nlinfit function of the statistics toolbox and a set of 
% initial parameters such as the one generated by init_coeffs.m.
% This function is used by ec50.m
%
% Copyright 2004 Carlos Evangelista 
% send comments to [e-mail]
% Version 1.0    01/07/2004

min=params4(1);
max=params4(2);
ec=params4(3);
hillc=params4(4);

x1=x(:,1);

yhat=min+(max-min)./(1+(x1/ec).^hillc);