gnuplot-py-users Mailing List for Gnuplot.py

chuck clark writes:
> I think my problem lies in the fact of I'm not sure which PlotItem
> type from gnuplot-py I should use.  I was originally trying to use
> Data but of course "12:01" can't be converted to a Numeric Float
> array.  So now I'm taking a step back and wondering if I need to
> create my own PlotItem types of Date, Time and DateTime to do this?
> [...]
> gnuplot> set xdata time
> gnuplot> set timefmt "%H:%M"
> gnuplot> set format x "%H:%M"
> gnuplot> set xrange ["12:00":"12:05"]
> gnuplot> plot "/home/cclark/test.dat" using 1:2

A PlotItem object represents a whole plot including all of the
associated data (if any), and the plot sub-command that has to be sent
to gnuplot (e.g., '"/tmp/sxhhfy" using 1:3 with linespoints').  You
can use any of the data-based PlotItems defined in the CVS version
(_InlineFileItem, _FIFOFileItem, or _TempFileItem); you just have to
call its constructor using the content that needs to be sent to
gnuplot as one of the arguments.  For example, this should work
(untested):

>>> content = """\
... 12:01    4.63
... 12:02    6.74
... 12:03    0.0
... 12:04    6.32
... """
>>> plot_item = PlotItems._TempFileItem(content, with='linespoints')
>>> g = Gnuplot.Gnuplot()
>>> g('set xdata time')
>>> g('set xdata time')
>>> g('set timefmt "%H:%M"')
>>> g('set format x "%H:%M"')
>>> g('set xrange ["12:00":"12:05"]')
>>> g.plot(plot_item)
>>> 

The only trick is getting your data into a "content" string that
gnuplot can understand.  You can do that any way you want.
PlotItems.Data() is now a helper function that does mainly that; you
can use it as a starting point.

I haven't decided whether to make the _InlineFileItem etc classes a
part of the Gnuplot.py published interface, which is why their names
start with '_'.  I might rename them before the next Gnuplot.py
release.

Michael

--
Michael Haggerty
hag...@jp...

Leo,
The mxdate package which Michael speaks of is a great package indeed and
handles datetime data very well and has almost any date/time functions you
could think of.  I think my problem lies in the fact of I'm not sure which
PlotItem type from gnuplot-py I should use.  I was originally trying to use
Data but of course "12:01" can't be converted to a Numeric Float array.  So
now I'm taking a step back and wondering if I need to create my own PlotItem
types of Date, Time and DateTime to do this?

I thought about doing as you say about converting my hh:mm:ss string into a
float but it isn't really clean because time is base 60 and not decimal and
I lose a lot of readability because suddenly my x-axis is not regular times
that the user would expect to see but some decimal representation of it.  If
I somehow try to preserve the time by making 12:01 into 1201 then I'll have
funny gaps from 1260 to 1300 and on every other hour.

Gnuplot itself handles Date/Time types as seen in the 3.7.1 manual.  If you
had the data below in a file called test.dat you could plot it in Gnuplot
with the following:

12:01    4.63
12:02    6.74
12:03    0.0
12:04    6.32

gnuplot> set xdata time
gnuplot> set timefmt "%H:%M"
gnuplot> set format x "%H:%M"
gnuplot> set xrange ["12:00":"12:05"]
gnuplot> plot "/home/cclark/test.dat" using 1:2

So I guess what I was wondering was if anyone had plotted date/time data
using gnuplot-py with the existing PlotItem types or if people who were more
familiar with the package than I am thought I'd need to come up with a new
type.  Any thoughts would be greatly appreciated.

cheers,
chuck