First impression from a new user

Community matplotlib-users
1

First impression from a new user
[Repost, sorry if you get this twice.]

Hi guys,

in my quest for a better gnuplot replacement, I came across matplotlib

yesterday.

I really like it, big thanks to the developers.

It was pretty easy to port over a gnuplot command file. There are

two things that could have been easier still though:

  • My data file consists of a date (in ISO format) and integers. Parsing

    the date was a bit of work. I understand that python’s datetime doesn’t

    provide any parsing of dates - but maybe matplotlib should have some

    functions for that then? FWIW, here is how gnuplot does this (adapted

    from http://t16web.lanl.gov/Kawano/gnuplot/datetime-e.html):

    set xdata time

    set timefmt “%Y-%m-%d”

    set format x “%Y-%m”

    In my matplotlib script, I’m now doing:

    mydate = [int(elem) for elem in vals_line[0].split(’-’)]

    datenums.append(date2num(datetime.date(mydate[0], mydate[1], mydate[2])))

    […]

    plotline = plot_date(datenums, data)

  • gnuplot has a plot style “steps”

    (http://t16web.lanl.gov/Kawano/gnuplot/intro/style-e.html) - I

    could only fake that with with extra “dummy” points in matplotlib

    as I understand it. It would be nice if matplotlib could do this

    for me.

Cheers,

Colin

2

You can use python's time module to parse dates, see time.strptime and time.strftime.

Jonathan

Marquardt, Colin wrote:

···

[Repost, sorry if you get this twice.]

Hi guys,

in my quest for a better gnuplot replacement, I came across matplotlib
yesterday.

I really like it, big thanks to the developers.

It was pretty easy to port over a gnuplot command file. There are
two things that could have been easier still though:

* My data file consists of a date (in ISO format) and integers. Parsing
  the date was a bit of work. I understand that python's datetime doesn't
  provide any parsing of dates - but maybe matplotlib should have some
  functions for that then? FWIW, here is how gnuplot does this (adapted
  from http://t16web.lanl.gov/Kawano/gnuplot/datetime-e.html):

     set xdata time
     set timefmt "%Y-%m-%d"
     set format x "%Y-%m"

  In my matplotlib script, I'm now doing:

     mydate = [int(elem) for elem in vals_line[0].split('-')]
     datenums.append(date2num(datetime.date(mydate[0], mydate[1], mydate[2])))
     [...]
     plotline = plot_date(datenums, data)

* gnuplot has a plot style "steps"
  (http://t16web.lanl.gov/Kawano/gnuplot/intro/style-e.html) - I
  could only fake that with with extra "dummy" points in matplotlib
  as I understand it. It would be nice if matplotlib could do this
  for me.

Cheers,
  Colin

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3

Here's a code snippet I found somewhere that demonstrates the use:

def make_datetime(s, fmt='%Y-%m-%d %H:%M'):
     '''convert string to datetime'''
     ts = time.mktime(time.strptime(s, fmt))
     return datetime.fromtimestamp(ts)

Warning, this is very slow, if you need to do a lot of conversions it will take some time.

Bill

Jonathan Taylor wrote:

···

You can use python's time module to parse dates, see time.strptime and time.strftime.

Jonathan

Marquardt, Colin wrote:

[Repost, sorry if you get this twice.]

Hi guys,

in my quest for a better gnuplot replacement, I came across matplotlib
yesterday.

I really like it, big thanks to the developers.

It was pretty easy to port over a gnuplot command file. There are
two things that could have been easier still though:

* My data file consists of a date (in ISO format) and integers. Parsing
  the date was a bit of work. I understand that python's datetime doesn't
  provide any parsing of dates - but maybe matplotlib should have some
  functions for that then? FWIW, here is how gnuplot does this (adapted
  from http://t16web.lanl.gov/Kawano/gnuplot/datetime-e.html):

     set xdata time
     set timefmt "%Y-%m-%d"
     set format x "%Y-%m"

  In my matplotlib script, I'm now doing:

     mydate = [int(elem) for elem in vals_line[0].split('-')]
     datenums.append(date2num(datetime.date(mydate[0], mydate[1], mydate[2])))
     [...]
     plotline = plot_date(datenums, data)

* gnuplot has a plot style "steps"
  (http://t16web.lanl.gov/Kawano/gnuplot/intro/style-e.html) - I
  could only fake that with with extra "dummy" points in matplotlib
  as I understand it. It would be nice if matplotlib could do this
  for me.

Cheers,
  Colin