View source for StepInterp

[[Category:Interpolation functions]]
[[Category:Doc Status D]] <!-- For Lumina use, do not change -->
 
= StepInterp( D,A,x,I ) =

Returns the element or slice of array A corresponding to the smallest value in D that is greater than or equal to x. D and A must both be indexed by I, and D must be increasing along index I. If x is greater than all values of D, returns the element for which D has the largest value.

If X is a single value, the result of Stepinterp() is an array indexed by all indexes of A except D’s index. If X is an array, the result of Stepinterp() is also indexed by the indexes of X.

StepInterp() is similar to [[Subscript]](u1, i, u2); however, [[Subscript]]() selects based on the index value being equal to x, while Stepinterp() selects based on the array value being greater than or equal to x. 

Stepinterp() can be used to perform table lookup.

= StepInterp( D,A,x,I, LeftLookup:True ) =

When the optional parameter, LeftLookup, is specified as true, StepInterp returns the element or slice of A corresponding to the largest value in D that is less than or equal to x.

The two graphs interpolate from the same set of ''(d,r)'' points, with different settings for ''LeftLookup''.

{|
| [[Image:Stepinterp-graph.png]] 
| [[Image:StepInterp2-graph.png]]
|-
! LeftLookup:False (default) 
! LeftLookup:True
|}

= See Also =

* The User Group Webinar [[Analytica_User_Group/Past_Topics#Step_Interpolation|Intro to Step Interpolation]] recording.
* [[LinearInterp]]
* [[CubicInterp]]
* [[Subscript]]