BinarySearchInterp

BinarySearchInterp (waveName, val)

The BinarySearchInterp function performs a binary interpolated search of the named wave for the value val. The returned value, pt, is a floating-point point index into the named wave such that waveName [pt] == val.

Details

BinarySearchInterp is useful for finding the point in an XY pair that corresponds to a particular X coordinate.

WaveName must contain monotonically increasing or decreasing values.

When the named wave does not actually contain the value val, BinarySearchInterp locates a value below val and a value above val and uses reverse linear interpolation to figure out where val would fall if a straight line were drawn between them. It includes that fractional amount in the resulting point index.

BinarySearchInterp returns NaN if val is not within the range of values in the wave, but would numerically be placed before the first value in the wave or after the last value in the wave.

Examples

Make/O data = {1, 2, 3.3, 4.9}      // Monotonic increasing
Print BinarySearchInterp(data,3)    // Prints 1.76923
Print data[1.76923]                 // Prints 3
Make/O data = {9, 4, 3, 1}          // Monotonic decreasing
Print BinarySearchInterp(data,2.5)  // Prints 2.25 
Print data[2.25]                    // Prints 2.5