Module function for getting model parameter values, etc.
Array_Type get_par([String_Type])
Error Return Values: NULL
Argument:
(1) Model name, or model parameter name (default all model parameters)
This function retrieves an array of structures, each of which contains
information about a defined model parameter. A typical structure looks
as follows:
sherpa> GAUSS[g]
sherpa> foo = get_par("g")
sherpa> print(foo[0])
name = g.fwhm
model = gauss1d
type = src
value = 10
min = 2.22507e-308
max = 1.79769e+308
delta = -1
units = NULL
frozen = 0
linked = 0
linkexpr = NULL
The fields of the structure are:
get_par Structure Fields
| name |
the name of the parameter |
| model |
the model that the parameter belongs to |
| type |
source/background-type (src) or instrument-type (inst) model |
| value |
the parameter value (either a number, or a string filename) |
| min |
the current (soft) lower bound on allowed parameter values |
| max |
the current (soft) upper bound on allowed parameter values |
| delta |
the initial step size for the parameter in fits (or -1 to use the default step size) |
| units |
parameter units, if known/appropriate |
| frozen |
if 1, the parameter value is frozen; if 0, it is thawed |
| link |
if 1, the parameter's value is linked to that of other parameter(s); if 0, it is not linked |
| linkexpr |
if the parameter is linked to other parameters, the expression showing how it is linked |
See the Sherpa command
CREATE for more information.
Get a parameter structure; change two fields; set back into
Sherpa:
sherpa> GAUSS[g]
sherpa> foo = get_par("g.pos")
sherpa> print(foo)
name = g.pos
model = gauss1d
type = src
value = 0
min = -3.40282e+38
max = 3.40282e+38
delta = -1
units = NULL
frozen = 0
linked = 0
linkexpr = NULL
sherpa> foo.value = 15.5
sherpa> foo.min = 0.0
sherpa> () = set_par(foo)
sherpa> SHOW g
gauss1d[g] (integrate: on)
Param Type Value Min Max Units
----- ---- ----- --- --- -----
1 fwhm thawed 10 1.1755e-38 3.4028e+38
2 pos thawed 15.5 0 3.4028e+38
3 ampl thawed 1 -3.403e+38 3.4028e+38
Here we loop through all the defined parameters
and display their name and current value:
sherpa> erase all
sherpa> paramprompt off
sherpa> xsmekal[gal]
sherpa> xsphabs[abs]
sherpa> ps = get_par()
sherpa> ps
Struct_Type[7]
sherpa> foreach(ps){p=();vmessage("Par %-14s = %g",p.name,p.value);}
Par gal.kT = 1
Par gal.nH = 1
Par gal.Abund = 1
Par gal.Redshift = 0
Par gal.Switch = 1
Par gal.norm = 1
Par abs.nH = 0.1
The initial set of lines are to set up two models
("gal", which is an
XSMEKAL model, and
"abs", which
is an XSPHABS model) with default
parameter values.
The ps variable is set here to
an array of 7 structures, which we loop through
using the S-Lang foreach function.
Each member of the array is looped through, and
stored in the variable p.
This variable is then used to get the parameters
name and value (p.name and
p.value respectively).
The whole 'foreach' statement must be
on one line since Sherpa does
not allow multi-line S-Lang statements.
This restriction does not apply to code
in a file executed via
evalfile().
Here we use a small S-Lang function we have written
to display parameter values. If the file
print_pars.sl contains:
define print_pars() {
variable pars = get_par();
if ( NULL == pars ) {
print( "No parameter values found!" );
return;
}
vmessage( "# Name model frozen value" );
foreach ( pars ) {
variable par = ();
vmessage( "%-20s %-10s %d %g",
par.name, par.model, par.frozen, par.value
);
}
}
then you can say:
sherpa> () = evalfile("print_pars.sl")
sherpa> erase all
sherpa> paramprompt off
sherpa> xsmekal[gal]
sherpa> xsphabs[abs]
sherpa> print_pars
# Name model frozen value
gal.kT xsmekal 0 1
gal.nH xsmekal 1 1
gal.Abund xsmekal 1 1
gal.Redshift xsmekal 1 0
gal.Switch xsmekal 1 1
gal.norm xsmekal 0 1
abs.nH xsphabs 0 0.1
although you may find either list_par()
or SHOW more useful.
- sherpa
-
autoest,
background,
create,
create_model,
createparamset,
fit,
freeze,
get_defined_models,
get_model_params,
get_models,
get_num_par,
get_stackexpr,
getx,
gety,
guess,
instrument,
integrate,
is_paramset,
jointmode,
kernel,
lineid,
linkparam,
mdl,
modelexpr,
modelstack,
nestedmodel,
noise,
paramprompt,
paramset,
pileup,
rename,
run_fit,
set_par,
set_paramset,
set_stackexpr,
source,
thaw,
truncate,
unlink
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