Last modified: December 2018

URL: http://cxc.harvard.edu/sherpa/ahelp/powlaw1d.html
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AHELP for CIAO 4.11 Sherpa v1

powlaw1d

Context: models

Synopsis

One-dimensional power-law function.

Syntax

powlaw1d

Description

It is assumed that the independent axis is positive at all points.


Example

>>> create_model_component("powlaw1d", "mdl")
>>> print(mdl)

Create a component of the powlaw1d model and display its default parameters. The output is:

mdl
   Param        Type          Value          Min          Max      Units
   -----        ----          -----          ---          ---      -----
   mdl.gamma    thawed            1          -10           10           
   mdl.ref      frozen            1 -3.40282e+38  3.40282e+38           
   mdl.ampl     thawed            1            0  3.40282e+38           

ATTRIBUTES

The attributes for this object are:

gamma

The photon index of the power law.

ref

As the reference point is degenerate with the amplitude, the alwaysfrozen attribute of the reference point is set so that it can not be varied during a fit.

ampl

The amplitude of the model.

Notes

The functional form of the model for points is:

f(x) = ampl * (x / ref)^(-gamma)

and for an integrated grid it is the integral of this over the bin.


Bugs

See the bugs pages on the Sherpa website for an up-to-date listing of known bugs.

See Also

models
polynom1d