Interesting problem - date arithmetics, compariosn

[Lars H. <lhe...@us...>]

 I came across an interesting problem, and have no (easy) solution for it:

 I would like to plot a datafile with time/date information

date val1 val2 ...
date val1 val2 ...
date val1 val2 ...

 but iwant to plot only certain dates. Via either "using" or the ternary
 operator, I need to compare a date against a given date and take action
 depending on the result. E.g. if the date from the data file is before
 Jan 01 2007, don't plot. In simple cases, and if the input can be
 controlled accordingly, this could be done via data index, but not
 necessarily in more complex cases.

 Similarily, I'd like to define a function based on time/date values. E.g.

 f(x) = ( x < Jan 01 2007 13:00  ? 30 : 40 )

 Any ideas how to achieve this? Unless I've missed some documentation, this
 is probably a nice little project for the post-4.2 era  :)