Optimization of parameters of the sigmoid function
Syntax:
[param]=sigm_fit(x,y)
that is the same that
[param]=sigm_fit(x,y,[],[],[]) % no fixed_params, automatic initial_params
[param]=sigm_fit(x,y,fixed_params) % automatic initial_params
[param]=sigm_fit(x,y,[],initial_params) % use it when the estimation is poor
[param]=sigm_fit(x,y,fixed_params,initial_params,plot_flag)
param = [min, max, x50, slope]
if fixed_params=[NaN, NaN , NaN , NaN] % or fixed_params=[]
optimization of "min", "max", "x50" and "slope" (default)
if fixed_params=[0, 1 , NaN , NaN]
optimization of x50 and slope of a sigmoid of ranging from 0 to 1
Additional information in the second output, STAT
[param,stat]=sigm_fit(x,y,fixed_params,initial_params,plot_flag)
Example:
%% generate data vectors (x and y)
fsigm = @(param,xval) param(1)+(param(2)-param(1))./(1+10.^((param(3)-xval)*param(4)))
param=[0 1 5 1]; % "min", "max", "x50", "slope"
x=0:0.1:10;
y=fsigm(param,x) + 0.1*randn(size(x));
%% standard parameter estimation
[estimated_params]=sigm_fit(x,y)
%% parameter estimation with forced 0.5 fixed min
[estimated_params]=sigm_fit(x,y,[0.5 NaN NaN NaN])
%% parameter estimation without plotting
[estimated_params]=sigm_fit(x,y,[],[],0)
R P (2021). sigm_fit (https://www.mathworks.com/matlabcentral/fileexchange/42641-sigm_fit), MATLAB Central File Exchange. Retrieved .
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Works perfectly and the instructions are clear.
Great function!
GDMFSOB Bloody brilliant! Thank you.
Works right out of the box. Thanks!
Works as expected!
Simple and effective. Similarly to polyfit-polyval, it would be great to include the related sigm_val function, to evaluate the generated sigmoidal curve.
tried using the function with my data and the givven example but in both recieved "Undefined function 'sigm_fit' for input arguments of type
'double'."
any thughts about it?
This requires a minmax() function - which toolbox is that in?