On 06/18/2010 07:31 AM, Ryan May wrote:
> On Thu, Jun 17, 2010 at 11:39 AM, Bill Eaton<e...@aeroantenna.com> wrote:
>> I'm struggling to figure out how to format my data so that I can use dates
>> as x-data.
> <SNIP>
>> I tried to import my own data. It looks like
>> 2005-03-04,0.923115796
>> 2005-03-05,0.915828724
>> 2005-03-06,0.442521474
>> 2005-03-07,0.997096213
>> 2005-03-08,0.867752118
Try matplotlib's mlab.csv2rec. It has a lot of magic built-in,
including automatic date recognition.
Eric
>> And to import, I use recarray
>> myarray = np.loadtxt(fullfile, dtype=[('date', '|O4'), ('ydata',
>> 'float')], delimiter = ',')
>> rx = myarray.view(np.recarray)
>>
>> Data imports fine. But when I go to plot, I get the following error
>> ValueError: setting an array element with a sequence.
>> WARNING: Failure executing file:<bogus.py>
>
> You need to give np.loadtxt a converter so that it converts that first
> column of strings into datetime objects:
>
> import numpy as np
> import matplotlib.pyplot as plt
> from matplotlib import dates
> from datetime import datetime
> from StringIO import StringIO
>
> s='''
> 2005-03-04,0.923115796
> 2005-03-05,0.915828724
> 2005-03-06,0.442521474
> 2005-03-07,0.997096213
> 2005-03-08,0.867752118'''
>
> dateparser = lambda s: datetime.strptime(s, '%Y-%m-%d')
> dt = np.dtype([('date', np.object),('ydata', np.float)])
> d = np.loadtxt(StringIO(s), dtype=dt, converters={0:dateparser},
> delimiter=',')
> plt.plot(d['date'], d['ydata'])
> plt.gca().xaxis.set_major_locator(dates.DayLocator())
> plt.gca().xaxis.set_major_formatter(dates.DateFormatter('%Y/%m/%d'))
> plt.show()
>
> Personally, I find it much easier to work with python datetime objects
> than any other form. You can
>
> Ryan
>
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