Last modified: December 2018

URL: http://cxc.harvard.edu/sherpa/ahelp/box2d.html
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AHELP for CIAO 4.11 Sherpa v1

box2d

Context: models

Synopsis

Two-dimensional box function.

Syntax

box2d

Description

The model is flat between the limits, where it is set to the ampl parameter. Outside this range the model is zero.


Example

>>> create_model_component("box2d", "mdl")
>>> print(mdl)

Create a component of the box2d model and display its default parameters. The output is:

mdl
   Param        Type          Value          Min          Max      Units
   -----        ----          -----          ---          ---      -----
   mdl.xlow     thawed            0 -3.40282e+38  3.40282e+38           
   mdl.xhi      thawed            0 -3.40282e+38  3.40282e+38           
   mdl.ylow     thawed            0 -3.40282e+38  3.40282e+38           
   mdl.yhi      thawed            0 -3.40282e+38  3.40282e+38           
   mdl.ampl     thawed            1 -3.40282e+38  3.40282e+38           

ATTRIBUTES

The attributes for this object are:

xlow

The lower edge of the box ( x0 axis).

xhi

The upper edge of the box ( x0 axis).

ylow

The lower edge of the box ( x1 axis).

yhi

The upper edge of the box ( x1 axis).

ampl

The amplitude of the box.

Notes

The functional form of the model for points is:

f(x0,x1) = ampl if xlow <= x0 <= xhi
                   ylow <= x1 <= yhi
         = 0       otherwise

and for an integrated grid it is:

f(x0lo,x0hi,x1lo,x1hi)
         = 0            if x0hi <= xlow or x0lo >= xhi
                        or x1hi <= ylow or x1lo >= yhi
         = ampl * g     where g is the fraction of the pixel
                        that falls within the region

This behavior is different to how the amplitude is handled in other models, such as Const2D .


Bugs

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

See Also

models
box1d, const2d, delta2d