matplotlib-users Mailing List for matplotlib

>>>>> "Chris" == Chris <Ch...@Fu...> writes:
 Chris> Dear friends, I just start to use matplotlib, which looks
 Chris> quite promising for me. I need to draw a couple of arrows
 Chris> in my 2D plot. Is there a simple way to get it work?
 Chris> Any suggustions are welcome.
I recommend creating an arrow class, derived from matplotlib.artist.Artist, that
contains a matplotlib.lines.Line2D for the arrow stem and a
matplotlib.patches.RegularPolygon with numVertices=3 for the arrow
head. You can control the rotation of the arrowhead with the
orientation argument. 
Once you have this class so defined, you can add it instances of it to
the axes with ax.add_artist(arrow).
I'll be happy to help out with a prototype if you have trouble. Take
a look at matplotlib.table.Cell, which John Gill wrote to support
tables. You can use this as a simple model for how to write new
artists (things that draw into a figure) composed of other artists.
It would be nice to have a fancy arrow class, that supported text
labeling, at the base, along the stem and at the arrowhead. You could
also consider a more sophisticated polygon other than a triangle for
the arrowhead.
Finally, if you needed to draw *a lot of arrows*, order of a thousand
or more (eg for direction fields), a
matplotlib.collections.PolygonCollection would be the way to go for
efficiency.
JDH

>>>>> "Greg" == Greg Wilson <gvw...@cs...> writes:
 Greg> Hi. I'm trying to graph the progress of a small software
 Greg> project over time. My program, and a sample data file, are
 Greg> attached. If I call ax.autoscale_view(), I get labels on my
 Greg> X axis, but the graph runs from 2002 to 2006, even though my
 Greg> data is only for Oct and Nov of 2004. If I comment out the
 Greg> autoscale_view() call, I get a much more reasonable range,
 Greg> but lose the ticks on the axis. What am I doing wrong?
The problem is you are using a YearLocator for your major ticks. This
will place ticks on every year, which is likely not what you want
since your date range is only a few days. 
I see that section of the code is a cut and paste from the date_demo
code. plot_date will try and pick the right tick locators and
formatters automatically. I suggest you just try plot_date with the
default (don't set the locator or formatter manually) and if you are
dissatisfied try setting locators and formatters appropriate for the
scale of data you are plotting - eg a DayLocator for the major ticks
and an hour locator for the minor ones (note you can configure the
locators to tick every day, every 2nd day, every 12th hour, etc...)
JDH

Hi. I'm trying to graph the progress of a small software project over
time. My program, and a sample data file, are attached. If I call
ax.autoscale_view(), I get labels on my X axis, but the graph runs from
2002 to 2006, even though my data is only for Oct and Nov of 2004. If I
comment out the autoscale_view() call, I get a much more reasonable range,
but lose the ticks on the axis. What am I doing wrong?
Thanks,
Greg