I have revised mk_strin so that it should work properly. Please tell me
if you find any problems.

To make a movie of your greyscale position/position maps in your
position/position/velocity data cube, download the lab 4 instructions
(which were revised yesterday) and look at the last page.

You can look at and modify the code for the 1d and 2d images I showed last night. Copy
the following three files to your area:

/home/global/ay121/labs/lab4/images/1dcolor_eg.idl
/home/global/ay121/labs/lab4/images/2dcolor_eg.idl
/home/global/ay121/labs/lab4/images/2dcolor_eg.sav