erf

Context: models

Synopsis

One-dimensional error function.

Syntax

erf

Description

The function is described at [1] .

Example

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

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

mdl
   Param        Type          Value          Min          Max      Units
   -----        ----          -----          ---          ---      -----
   mdl.ampl     thawed            1            0  3.40282e+38           
   mdl.offset   thawed            0            0  3.40282e+38           
   mdl.sigma    thawed            1        1e-10           10

ATTRIBUTES

The attributes for this object are:

Attribute	Definition
ampl	The amplitude of the model.
offset	The offset of the model.
sigma	The scaling factor.

Notes

The functional form of the model for points is:

f(x) = ampl * erf((x - offset) / sigma)

erf(y) = (2 / sqrt(pi)) Int_0^y exp(-t^2) dt

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

References

[1] http://mathworld.wolfram.com/Erf.html

Bugs

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