Re: [Matplotlib-users] histogram of evetns, unix time

[John H. <jdh...@ac...>]

>>>>> "Jiri" == Jiri Polcar <po...@ph...> writes:

    Jiri>     Hallo, I have array (ut) of numbers represents unix time
    Jiri> (number of seconds from 1. 1. 1970) of some evenets:

    Jiri>     ...  1127164705 1127199439 1127199439 1127199494
    Jiri> 1127199640 1127199651 ...

matplotlib interprets dates as days since 0000-00-00 rather than
seconds since the epoch, so you need to convert epoch time with the
epoch2num function in matplotlib.dates and then plot with plot_dates

  dnum = epoch2num(ut)
  plot_date(dnum, y)

    Jiri> I want to plot histogram of this events. I used:

    Jiri>     from pylab import * n, bins, patches = hist( ut, 50 )
    Jiri> setp(patches, 'facecolor', 'g', 'alpha', 0.75) axis([
    Jiri> 0.9999*amin(ut), 1.0001*amax(ut), 0, 1.1*amax(n) ]) show()

    Jiri> But I want to display labels on x-axis's tics as a date
    Jiri> human readable date (for example "Dec 13").

If you are not happy with the default date ticking and formatting
provided by plot_date, you can set you own date tick locator and
formatter.  Read about tick locators and formatters here

  http://matplotlib.sf.net/matplotlib.ticker.html

and date specific tick locator and formatters here

  http://matplotlib.sf.net/matplotlib.dates.html

and in the online Users Guide.  See also the *date*.py examples in the
examples directory, http://matplotlib.sf.net/examples


    Jiri> It works perfectly. Thanke you.  How can I set x-axis range?
    Jiri> In case of my real data the histogram is not "centred" and
    Jiri> epmty spaces was too huge. In my previous way works:

    Jiri>     axis([ 0.9999*amin(ut), 1.0001*amax(ut), 0, 1.1*amax(n)

Use epoch2num again

  xlim(epoch2num(amin(ut)), epoch2num(amax(ut)))

Note that if you pick the appropriate date locator (which plot_date
tries to do for you automagically), you probably do not need to set
the xlim explicitly, since this is the job of the tick locator's
autoscale method.

JDH