[time-nuts] time-nuts Digest, Vol 33, Issue 29

Christopher Hoover ch at murgatroid.com
Wed Apr 11 13:39:50 EDT 2007


"Tom Van Baak" <tvb at LeapSecond.com> wrote: 
> If anyone has other favorite plotting methods, please let
> us know.

Although I use and favor gnome as my desktop, I've been using kde's kst
plotting package.  It is not bad, which for me, discussing a software
package, is an above average endorsement.  There are some rough edges, for
sure, but it draws nice plots, handles multiple data files and live file
updates fairly well, and has some OK fitting and filtering capabilities.
(It is pluggable, too -- one could imagine an adev plugin.)  See the
attached png for an example(1).

The rest of my kit includes stable32 and a bunch of perl, awk and C++ code.
I'd like to put a proper set of tools together out as a package some day.

Incidentally, I've found that it is important to be quite careful with your
floating point handling when representing a quantity of seconds with
picosecond resolution in an IEEE 64-bit float.

This is where exact float support or a big float package comes in handy.

Some languages may support exact/big floats natively (some scheme
implementations, nickel[sic]).  For others, support is often in a library.
Math::BigFloat does the trick for Perl.   See the attached perl file, which
does 5313x conversion without any loss of any precision.

An explicit rational representation also works, but it is handy to have a
library or language support to handle the arithmetic as it is tricky to get
it both right and fast.   For C++, boost's rational support is quite good
(as is most everything in boost).

-ch

(1) The anomaly in the plot is something that hit all my gps receivers,
including 2 Z3801a's, an m12+, and, as in the graph, an m12t.  Odd, huh?

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