Cubic Interpolation of a 1-D function.



  YI=ICUBIC(Y,XI) returns the value of the 1-D function Y at the

  points XI using cubic interpolation. length(YI)=length(XI). XI is

  an index into the vector Y. Y is the value of the function

  evaluated uniformly on a interval. If Y is a matrix, then

  the interpolation is performed for each column of Y.



  If Y is of length N then XI must contain values between 1 and N.

  The value NaN is returned if this is not the case.



  YI = ICUBIC(X,Y,XI) uses the vector X to specify the coordinates

  of the underlying interval. X must be equally spaced and

  monotonic. XI must lie within the coordinates in X.