1-D data interpolation (table lookup).

  YI = INTERP1(X,Y,XI) returns vector YI containing elements

  corresponding to the elements of XI and determined by interpolation

  within vectors X and Y.



  Interpolation is the same operation as "table lookup".  Described in

  "table lookup" terms, the "table" is [X,Y] and INTERP1 "looks-up"

  the elements of XI in X, and, based upon their location, returns

  values YI interpolated within the elements of Y.



  INTERP1 performs multiple output table lookup if Y is a matrix.

  If Y is a matrix with length(X) rows, and N columns, INTERP1

  returns a length(XI)-by-N matrix YI containing the multi-output 

  table lookup results.



  By default, INTERP1 uses linear interpolation.

  YI = INTERP1(X,Y,XI,'method') specifies alternate methods.

  Available methods are:



    'linear' - linear interpolation

    'spline' - cubic spline interpolation

    'cubic' - cubic interpolation



  All the interpolation methods require that X be monotonic. The

  'cubic' method also requires that the points in X be equally-spaced.



  For example, generate a coarse sine curve and interpolate over a

  finer abscissa:

                   x = 0:10; y = sin(x);

                   xi = 0:.25:10;

                   yi = interp1(x,y,xi);