Last modified: December 2018

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

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:

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


Bugs

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

See Also

models
erfc