fit_sigm 2.0.3 © 2006-2012 Turku PET Centre, University of Turku
Non-linear fitting of the Hill function (sigmoid function) to a (xi,yi)
curve data. Optionally, a background term B is added to the function:
f(x) = (A * x^n ) / ( x^n + K ) + B , where A>=0, K>0, n>0, B>=0
Function for estimating EC50 from sigmoidal dose-response curve is obtained
by rearranging and marking n=HillSlope, A=Top-Bottom, B=Bottom, and
K=EC50^n :
f(x) = Bottom + (Top-Bottom)/(1 + (EC50/x)^HillSlope)
With HillSlope constrained to 1 (see options below) the function reduces to
unconstrained one site binding hyperbola, f(x)=Top*x/(EC50+x).
Usage: fit_sigm [Options] <Data file> <Fit file>
Options:
-EC50
EC50 is estimated by fitting sigmoidal dose-response curve function
when drug concentrations are on a linear scale (not on a log scale);
By default, parameter Top is fitted and Bottom is constrained to 0,
which can be changed with options (see below)
-w1 All weights are set to 1.0 (no weighting); by default, weights in
data file are used, if available
-wf
Weight by sampling interval
-n=<value>
Parameter n or HillSlope is constrained to the given value; set -n=1
to fit one site binding hyperbola
-B Parameter B or Bottom is fitted; by default B=0
-B=<value>
Parameter B or Bottom is constrained to the given value
-A=<value>
Parameter Top is constrained to the given value; currently this option
does not affect parameter A in the default function
-MRL
Error is returned if MRL check is not passed
-res=<Filename>
Fitted parameters are also written in result file format (3)
-svg=<Filename>
Fitted and measured TACs are plotted in specified SVG file
-fit=<Filename>
Fitted TACs are written in DFT format
-h or --help
Print this message and exit
--version or --build
Print software build information and exit
--silent
Program works silently, printing only error and warning messages
--verbose
Program prints more information about what it is doing.
Data file must contain at least 2 columns, sample times (or concentrations)
and measurement values (or receptor occupancies).
Weights can be specified as usual if data is in DFT format (1).
Program writes the fit start and end times, nr of points, WSS,
and parameters of the fitted function to the fit file (2).
References:
1.
http://www.turkupetcentre.net/analysis/doc/format_dft.html
2.
http://www.turkupetcentre.net/analysis/doc/format_fit.html
3.
http://www.turkupetcentre.net/analysis/doc/format_res.html
See also:
fit_hiad,
fit_ppf,
fit_exp,
fit_ratf,
fit2dat,
dft2csv
Keywords: curve fitting, Hill function, sigmoid, EC50, dose-response curve
This program comes with ABSOLUTELY NO WARRANTY. This is free software, and
you are welcome to redistribute it under GNU General Public License.