Re: Plotting date on xaxis

[Dan Davison <davison@stats.ox.ac.uk>]

Johan Ekh <ekh.johan@gmail.com> writes:

> Thanks guys,
> the babel version worked perfect so I didn't try the other one thanks!
> Would it be possible to use python and matplotlib with babel instead of
> gnuplot?
> If so, could you just indicate how such a src code block would look like?

Hi Johan,

I've never used matplotlib, but here's a start. Firstly, one thing I
notice is that org-babel-python currently doesn't like the column names
on the table (I'll add it to our TODO list). So if we make a table like
this, without the header:

#+results: my-table-nohdr
| 2010-02-21 | 95.0 |
| 2010-02-22 | 93.0 |
| 2010-02-23 | 92.0 |
| 2010-02-24 | 91.5 |
| 2010-02-25 | 91.0 |
| 2010-02-26 | 92.0 |

Then pass the data into python and have a look at what we've got:

#+begin_src python :var data=my-table-nohdr :results output
print str(data)
#+end_src

#+results:
: [['2010-02-21', 95.0], ['2010-02-22', 93.0], ['2010-02-23', 92.0], ['2010-02-24', 91.5], ['2010-02-25', 91.0], ['2010-02-26', 92.0]]

So if you know how to use matplotlib to create your plot using that list
of lists, then you should be set. To get output to file you will need to
use something like :file pyplot.png, *and* arrange that your code writes
the graphical output to pyplot.png. A link to pyplot.png will be
inserted in the org buffer.

Given my ignorance of gnuplot and matplotlib, I would use R. Unlike
python, but like gnuplot, the graphical output is automatically sent to
the specified file, without having to explicitly tell R to so so:

#+begin_src R :var d=my-table :file R-plot.png
  plot(as.Date(d$Date), d$Kg, ylab="Kg", type="b")
#+end_src

#+results:
[[file:R-plot.png]]

Dan

>
> Babel seems super cool!
>
> /Johan
>
> On Tue, Feb 23, 2010 at 3:47 PM, Eric Schulte <schulte.eric@gmail.com> wrote:
>
>     Hi Johan,
>
>     You could try plotting your table using standard org-mode date formats
>     which org-plot will understand without any need to specify a timefmt
>     string.
>
>     #+PLOT: title:"Weight" ind:1 deps:(2) type:2d with:linespo set:"xdata time"
>     set:"yrange [90:]"
>     | Date             |   Kg |
>     |------------------+------|
>     | <2010-02-21 Sun> | 95.0 |
>     | <2010-02-22 Mon> | 93.0 |
>     | <2010-02-23 Tue> | 92.0 |
>     | <2010-02-24 Wed> | 91.5 |
>     | <2010-02-25 Thu> | 91.0 |
>     | <2010-02-26 Fri> | 92.0 |
>
>     Alternatively if you want more control over your plots and more direct
>     access to gnuplot you can use org-babel to pass your table directly to
>     gnuplot as follows.
>
>     #+results: my-table
>     |       Date |   Kg |
>     |------------+------|
>     | 2010-02-21 | 95.0 |
>     | 2010-02-22 | 93.0 |
>     | 2010-02-23 | 92.0 |
>     | 2010-02-24 | 91.5 |
>     | 2010-02-25 | 91.0 |
>     | 2010-02-26 | 92.0 |
>
>     #+begin_src gnuplot :var data=my-table
>      set xdata time
>      set timefmt '%Y-%m-%d'
>      set yrange [90:]
>      plot data using 1:2 with linespoints title 'Kg'
>     #+end_src
>
>     Best -- Eric
>
>     Johan Ekh <ekh.johan@gmail.com> writes:
>
>     > Hi all,
>     > I try to plot a table looking like this
>     >
>     >      |       Date    |   Kg |
>     >      |-----------------+--------|
>     >      | 2010-02-21 | 95.0 |
>     >      | 2010-02-22 | 93.0 |
>     >      | 2010-02-23 | 92.0 |
>     >      | 2010-02-24 | 91.5 |
>     >      | 2010-02-25 | 91.0 |
>     >      | 2010-02-29 | 92.0 |
>     >      |                  |        |
>     >
>     > with the dates on the xaxis using
>     >
>     > #+PLOT: title:"Weight" ind:1 deps:(2) type:2d with:linespo set:"xdata
>     time" timefmt:%Y-%m-%d
>     > set:"yrange [90:]"
>     >
>     > but no plot is generated. If I remove <set:"xdata time">, the plot is
>     generated but without
>     > interpreting the dates as dates.
>     >
>     > Can anyone see what I do wrong?
>     >
>     > Thanks in advance,
>     >
>     > Johan
>     >
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