stdAlpha confidence level in units of standard deviation
Default value given in config.analyses.PLE.confLevelInUnitsOfStd,
usually 1 corresponding to a 68% confidence interval.
steppingMode 1 = direct step, 2 = progressive step
Default value given in config.analyses.PLE.steppingMode, usually 1.
Description
0. Adjust default values specified in the configuration.
config.analyses.PLE.*
1. Load the desired model(s) and data-set(s) into PottersWheel and calibrate the
parameters to best possible values. To get an overview about the parameters
incorporated in the model, execute pwInfo at the command line. PLE will
consider all fitted parameters. If necessary, use the command pwFixParameters
to free or fix parameters. Use either integrator 14 (CVODES) with
active Jacobian calculation for integration and optimization or
integrator 1 (RADAU5) with the fast integration scheme (pwFastIntegration(true)).
2. Initialise PLE using pwPleInit or open the PLE GUI using pwPLEgui.
All computed results will be stored in the subfolder PLE-yyyymmddTHHMMSS.
Continue within the GUI or apply the following commands.
3. To estimate the profile likelihood for all free parameters run pwPleCalculate
For a specific parameter run pwPleCalculate(i) where i refers to the number
of the parameter as listed by pwInfo.
Further arguments to pwPleCalculate(i, a, b, c, d, e) are:
a) maximum number of steps in increasing and decreasing direction, default = 100
b) aspired chi-square increase between two sampling steps,
measured in percentage of delta-alpha, default = 0.1
c) minimum step size in %, default = 0.01% of the parameter value
d) maximum step size in %, default = 50% of the parameter value
e) flag to stop the estimation, if the sampled parameter is increased or
decreased above or below its parameter bounds, default = true
4. Execute pwPlePrint to get a summary of the results, including an automatically
generated flag IDflag stating the type of identifiability. LowerPL and UpperPL
indicate likelihood based confidence intervals sigma^{pm, PL}, LowerHes and UpperHes
confidence intervals approximated by the inverse of the Hessian matrix sigma^{pm, Hes}
and Rel.PL and Rel.Hes the relative size of the confidence intervals (sigma^+ - sigma^-)/(2�
theta_i).
5. Execute pwPlePlot(i) to generate a figure showing the profile likelihood Chi^2_{PL}
PL(theta_i) and the corresponding changes in the other parameters.
6. Execute pwPlePlotMulti to generate a figure showing an overview of all so far
calculated profile likelihoods.
7. Execute pwPlePlotRelations(js) where js is a vector of parameter indices, to
generate a scatterplot of parameters to reveal functional relations. This is most
convenient for two or three indices. One index generates a histogram and if js
is omitted, a matrix plot is produced.
8. Execute pwPleTrajectories(i) to plot trajectories corresponding to parameter
values sampled for the profile likelihood Chi^2_{PL}(theta_i). This depicts model
variability due to uncertainties in this parameter.
Reference
Raue A., Kreutz C., Maiwald T., Bachmann J., Schilling M., Klingmueller U. and Timmer J.
'Structural and practical identifiability analysis of partially observed dynamical
models by exploiting the profile likelihood.'
Bioinformatics, 2009
Implementation within PottersWheel by Andreas Raue and Thomas Maiwald.