LinearInterp
LinearInterp(d,r,x,I)
Uses linear interpolation to determine the value of a piecewise linear function at x. The piecewise curve is determined from a set of points, (d,r) indexed by I, which represent the vertices of the curve. (Think of d as the domain, or horizontal axis, and r as the range, or vertical axis, when thinking about these points). The array d must be strictly increasing.
LinearInterp finds two two points in d that x lands between -- i.e.,
- d[@I=j] <= x <= d[@I=j+1]
and then interpolates between the two points (d[@I=j],r[@I=j]) and (d[@I=j+1],r[@I=j+1]) for that value of x. You can pass an array of values in for x to find many points on the curve at once.
For values of x landing to the left or right of all points, LinearInterp extrapolates by assuming the function is a constant value, equal to the leftmost or rightmost value in r.
For release 4.1.1 or earlier, the parameters must be strictly numeric. For releases after this, d and r may contain Null values, in which case these points are ignored, with the interpolating occurring only between non-null points. Also, when x is null or when there are no non-null data points, the result is null.
Library
Array functions
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