Re: [Matplotlib-users] ploting with dates?

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

>>>>> "Jeff" == Jeff Peery <jef...@se...> writes:

    Jeff> Hello, I am trying to learn how to plot using dates. In my
    Jeff> code I'm basically trying to do the following:

    Jeff> t1 = ['05/05/2005', '05/06/2005', '05/07/2005',
    Jeff> '05/08/2005']

    Jeff> t3 = [1,2,3,4]

    Jeff> #plot data self.axes.plot_date(t1, t3, 'bo')

    Jeff> this doesn't work for me. What does the input for plot_date
    Jeff> need to look like? Thanks.


From the plot_date help

plot_date(self, d, y, fmt='bo', tz=None, **kwargs)
    PLOT_DATE(d, y, converter, fmt='bo', tz=None, **kwargs)
     
    d is a sequence of dates represented as float days since
    0001-01-01 UTC and y are the y values at those dates.  fmt is
    a plot format string.  kwargs are passed on to plot.  See plot
    for more information.
     
    See matplotlib.dates for helper functions date2num, num2date
    and drange for help on creating the required floating point dates
     
    tz is the timezone - defaults to rc value


The snippet below should get you started...

  from matplotlib.dates import date2num
  from datetime import datetime

  def ymd(s):
      m,d,y = [int(num) for num in s.split('/')]
      return y,m,d

  t1 = ['05/05/2005', '05/06/2005', '05/07/2005', '05/08/2005']

  datenums = date2num([datetime(*ymd(s)) for s in t1])

See also examples/date_demo*.py in the matplotlib src distro or zipped
up here

http://matplotlib.sourceforge.net/matplotlib_examples_0.80.zip

JDH