FUNCTION: interp(y,x,u) PURPOSE: Linearly Interpolates vectors with an irregular grid. INTERP is functionally the same as INTERPOL, however it is typically much faster for most applications. USAGE: result = interp(y,x,u) INPUTS: Y: The input vector can be any type except string. X: The absicissae values for Y. This vector must have same # of elements as Y. The values MUST be monotonically ascending or descending. U: The absicissae values for the result. The result will have the same number of elements as U. U does not need to be monotonic. KEYWORDS: NO_CHECK_MONOTONIC: set this keyword to skip the check for monotonic data. INDEX: Set to named variable to return the index of the closest x less than u. (same dimensons as u) NO_EXTRAPOLATE: Set this keyword to prevent extrapolation. INTERP_THRESHOLD: Set to minimum allowed gap size. CREATED BY: Davin Larson 4-30-96 FILE: interp.pro VERSION: 1.15 LAST MODIFICATION: 02/04/17