steppar

           compute confidence range/contour for fit

           cafe

           steppar ,param1["[min;max;step]"][:group1],
                    param2["[min;max;step"]][:group2][,/verbose][,/plot]

           param1,param2 - the parameters to compute the confidence
                           range/plot for. This may be either:
                           - The absolute parameter number in the
                             current model.
                           - A string designating the parameter
                             name. The parameter name is usually
                             "model:parname".
                           If more than two parameter is specified an
                           error will be raised.
            min          - (optional) Defines start point of range to
                           be computed (for each parameter
                           defined). Default is parameter value less
                           3* error value (i.e. 3*sigma).
            max          - (optional) Defines end point of range to
                           be computed (for each parameter
                           defined). Default is parameter value plus
                           3* error value (i.e. 3*sigma).
            step         - number of points to use to step from <min>
                           to <max>. Default is 20.
            group1       - The group number in which the parameter 1
                           should be looked for. The same applies for
                           parameter 2/group2.

           Because the computation of contour levels
           immediately influence the plotting of contour
           plot style it is possible to set the contour grid
           ranges with the setplot command. The parameters
           are:
             par1min   - Start value as above for parameter 1, min
             par1max   - End value as above for parameter 1, max
             par1step  - Step number as above for parameter 1, step
             par2min   - Start value as above for parameter 2, min
             par2max   - End value as above for parameter 2, max
             par2step  - Step number as above for parameter 2, step

           This command initiates a step of 1 or 2 parameters to step
           through while fixing this parameter, perform a fit while
           kepping this parameter fixed and compute the chi^2 value.
           These values are stored in a separate group (29) and could
           be used later for a contour plot (refer plot,steppar)
           which shows the range of a confidence level correlating
           different parameter.
           If only one parameter is given the contour plot/steppar
           plot displays the varying chi^2 values.
           If a plot should be performed the command "plot" should be
           called with the plot style "steppar" (for one parameter)
           or "steppar2" (for 2 parameters) after performing the
           computation of the steppar grid values.
           It is also possible to use the "data"/"data2" plot style
           but then no confidence ranges are shown.
           For fitting following parameter rules are used:
           - if a parameter is frozen (fixed flag = 1) the parameter
             will not be touched while fitting.
           - if a parameter is tied to another parameter this
             parameter will copy the latter parameter value (in case
             of expressions the value will be mapped with this
             expression).
           - groups which contain a model but no valid data points
             are ignored. In case of the selected flag (s.a.) only
             selected data points are taken into account, i.e. if no
             data points are selected the group is ignored.
           - groups which contain valid data points but no model are
             ignored.

           plot    - plot the contour (as a sort of preview). The
                     plot could not be printed out with the plotout
                     command.
           verbose - report fit process.
           selected- compute steppar for selected data points only
           nodata  - Take also models into account which are in
                     groups containing no data. May be usefull
                     when building complex models refering one to
                     other.

           All options may be set with the "set" command. The
           command prefix is "steppar".

           Long lasting steppar processes may be interrupted with
           "Ctrl-G". (Not possible in idlwave).

           Stores the steppar values in group 9 if this group is free.

           > model, "parabel", 1
           > fit
           > steppar, 1[0;1;30],2[3;4;10]
                 -> compute steppar plot for parameter 1+2,
                    ranging from 0..1 (30 steps) for parameter 1 and
                    from 3..4 (20 steps) for parameter 2.
           > plot, steppar2
                 -> show result

           $Id: cafe_steppar.pro,v 1.18 2004/05/27 07:33:38 goehler Exp $

[Home Page] [Software, Documentation] [IDL Documentation] [Quick Reference] [Feedback]