Last modified: December 2018

URL: http://cxc.harvard.edu/sherpa/ahelp/polynom2d.html
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AHELP for CIAO 4.11 Sherpa v1

polynom2d

Context: models

Synopsis

Two-dimensional polynomial function.

Syntax

polynom2d

Description

The maximum order of the polynomial is 2.


Example

>>> create_model_component("polynom2d", "mdl")
>>> print(mdl)

Create a component of the polynom2d model and display its default parameters. The output is:

mdl
   Param        Type          Value          Min          Max      Units
   -----        ----          -----          ---          ---      -----
   mdl.c        thawed            1 -3.40282e+38  3.40282e+38           
   mdl.cy1      thawed            0 -3.40282e+38  3.40282e+38           
   mdl.cy2      thawed            0 -3.40282e+38  3.40282e+38           
   mdl.cx1      thawed            0 -3.40282e+38  3.40282e+38           
   mdl.cx1y1    thawed            0 -3.40282e+38  3.40282e+38           
   mdl.cx1y2    thawed            0 -3.40282e+38  3.40282e+38           
   mdl.cx2      thawed            0 -3.40282e+38  3.40282e+38           
   mdl.cx2y1    thawed            0 -3.40282e+38  3.40282e+38           
   mdl.cx2y2    thawed            0 -3.40282e+38  3.40282e+38           

ATTRIBUTES

The attributes for this object are:

c

The constant term.

cy1

The coefficient for the x1 term.

cy2

The coefficient for the x1^2 term.

cx1

The coefficient for the x0 term.

cx1y1

The coefficient for the x0 x1 term.

cx1y2

The coefficient for the x0 x1^2 term.

cx2

The coefficient for the x0^2 term.

cx2y1

The coefficient for the x0^2 x1 term.

cx2y2

The coefficient for the x0^2 x1^2 term.

Notes

The functional form of the model for points is:

f(x,x1) = c + cx1 * x0 + cx2 * x0^2 +
              cy1 * x1 + cy2 * x1^2 +
              cx1y1 * x0 * x1 +
              cx1y2 * x0 * x1^2 +
              cx2y1 * x0^2 * x1 +
              cx2y2 * x0^2 * x1^2

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