Add contour labels to a contour plot.

  CLABEL(CS) adds height labels to the current contour plot

  using the contour structure CS output from the CONTOURXAOYTS routine.

  The label positions are selected randomly.  For example:



     cs = contour(rand(10)); clabel(cs)



  CLABEL(CS,V) labels just those contour levels given in

  vector V.  The default action is to label all known contours.



  CLABEL(CS,'manual') places contour labels at the locations

  clicked on with a mouse.  Pressing the return key terminates

  labeling.  Use the space bar to enter contours and the arrow

  keys to move the crosshair if no mouse is available.