
   peak [-q] (x) (y) [startx endx]

   Determines the peak of the y vector between starx and endx
    or between the extrema of the x vector (default)

   -q: quiets the script (no output to the window)

   Outputs:
    $peakval: Value of the peak
    $peakpos: X value corresponding to the peak value
    $peaknum: Index of the peak value
