[las_users] still-a-newbie time axis question

[John Graybeal <graybeal@xxxxxxxxx>]

I'm sure this is endlessly documented, but with apologies, I need a more direct answer than I have found. Hopefully it is easy to answer.

If I have profile data with the following characteristics:
 a) multi-column data with one column = floating days since 1900,
 b) irregularly spaced points (samples are 0.25 seconds apart; profiles from 4 to many hours apart), and
 c) many many points (say hundreds of thousands), then
How do I plot all the points on one plot with nicely labeled X axis?  (Of course I want to maintain fidelity to the slowly changing sample time, so a ZT plot for just a few profiles would show a bit of time drift over the profile.)

I've made a plot that is visually desirable with 

yes? FILE/FORMAT=DELIMITED/DELIM="\t"/VARIABLES="a,b,fdays1900,c,d"/SKIP=1 DataTest.dat
yes? go polymark poly/key fdays1900 depth temp circle .2

(Well, sometimes I have to enter the second command twice, but that isn't today's topic.)

I haven't quite grokked the magic combination of commands that creates a nicely gridded time axis along the lines of
  yes? define axis/t="1-JAN-2007":"1-JUL-2007":30/UNITS=days timeaxis
, and then links timeaxis to fdays1900, or rather vice versa, and then links all the other data through fdays1900 to the time axis (but I think that last piece is free).  Can someone take pity and offer the one or two lines I'm missing that will transform my polymark axis from fdays into formatted date/time strings?

Oh yeah, I'm on a Mac so ferret 5.7 is all I have to work with for now....

John


-- 
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John Graybeal   <mailto:graybeal@xxxxxxxxx>  -- 831-775-1956 
Monterey Bay Aquarium Research Institute
Marine Metadata Initiative: http://marinemetadata.org   ||  Shore Side Data System: http://www.mbari.org/ssds