Synopsis
One-dimensional log-parabolic function.
Syntax
logparabola
Example
>>> create_model_component("logparabola", "mdl") >>> print(mdl)
Create a component of the logparabola model and display its default parameters. The output is:
mdl Param Type Value Min Max Units ----- ---- ----- --- --- ----- mdl.ref frozen 1 -3.40282e+38 3.40282e+38 mdl.c1 thawed 1 -3.40282e+38 3.40282e+38 mdl.c2 thawed 1 -3.40282e+38 3.40282e+38 mdl.ampl thawed 1 0 3.40282e+38
ATTRIBUTES
The attributes for this object are:
Attribute | Definition |
---|---|
ref | The reference point for the normalization. |
c1 | The power-law index (gamma). |
c2 | The curvature of the parabola (beta). |
ampl | The amplitude of the model. |
Notes
The functional form of the model for points is:
f(x) = ampl * (x / ref) ^ (-c1 - c2 * log_10 (x / ref))
The grid version is evaluated by numerically intgerating the function over each bin using a non-adaptive Gauss-Kronrod scheme suited for smooth functions [1] , falling over to a simple trapezoid scheme if this fails.
References
- [1] https://www.gnu.org/software/gsl/manual/html_node/QNG-non_002dadaptive-Gauss_002dKronrod-integration.html
Bugs
See the bugs pages on the Sherpa website for an up-to-date listing of known bugs.