Brain Imaging & Analysis Center

usage: y = interpolate(x,stdx,stdy,flag)

INTERPOLATE uses a standard curve, defined by the two arrays STDX and STDY, which convert a third set of values, X, to output values Y. The conversion involves first finding the STDX values on either side of each X value (or the two nearest values if X is outside the range of STDX). The Y values are then generated based on the STDY values corresponding to those nearest STDX values. INTERPOLATE normally does a linear local interpolation of Y values based on a standard curve that need not be linear. This type of interpolation can be modified by using the FLAG option as:

                 FLAG:  0 - linear interpolation (default)
                        1 - set Y2 to the STDY value corresponding to the closest STDX
                                value that is at or below X2
                        2 - set Y2 to the STDX value corresponding to the closest STDX
                                value that is at or below X2
                        3 - do a cubic spline interpolation instead of a simple linear
                                interpolation
                        4 - fill Y2 with linearly increasing values (e.g. 0,1,2,...) 
                                with the counting base reset to the STDY value each time 
                                the X value crosses one of the STDX values

The length of the arrays STDX and STDY must be the same. The number of Y output values generated will be the same as the number of X input values.

See Also:
SPLINE(2)

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