********Problem solved!**********
Thanks for all the tipps, but they didn't fix the problem. There never
was a problem with usecols or something. My mistake was, that I've
used the plot-script-file as the datainput-file, by accident.
Sorry for wasting your time with this.
I think it's too late (00:34 AM here), I have to go to bed and get
some sleep....
Manuel
2009/11/16 Gökhan Sever <gokhanse...@gmail.com>:
>
>
> On Mon, Nov 16, 2009 at 4:34 PM, Manuel Wittchen <manuel.wittc...@gmail.com>
> wrote:
>>
>> Hi,
>>
>> I'm trying to make my first matplotlib-plot from a datafile. The
>> datafile is tab-separated and looks like this:
>> # x-axis y-axis
>> 0 1
>> 1 2
>> 2 3
>> 3 4
>> 4 5
>> 5 6
>>
>> So my ploting-script is:
>>
>> #!/usr/bin/env python
>> from pylab import *
>> import numpy as np
>>
>> inputfile = '/home/manu/matplotlib-examples/simple_plot.py'
>>
>> x,y = np.loadtxt(inputfile, dtype='float', comments='#',
>> delimiter="\t", converters=None, skiprows=0, usecols=(0,1),
>> unpack=True)
>> plot(x, y, linewidth=1.0)
>> xlabel('time (s)')
>> ylabel('voltage (mV)')
>> title('About as simple as it gets, folks')
>> grid(True)
>> show()
>>
>> It worked fine for me once, but as I tried to start the script again I
>> get an IndexError:
>>
>> Traceback (most recent call last):
>> File "./simple_plot.py", line 7, in <module>
>> x,y = np.loadtxt(inputfile, dtype='float', comments='#',
>> delimiter="\t", converters=None, skiprows=0, usecols=(0,1),
>> unpack=True)
>> File "/usr/lib/python2.6/dist-packages/numpy/lib/io.py", line 486, in
>> loadtxt
>> vals = [vals[i] for i in usecols]
>> IndexError: list index out of range
>>
>> Seems to me that usecols has "to much input" (don't know how to call
>> it), but why did it work before?
>
> This is an interesting behaviour. I don't exactly know why it happens as you
> described, but If you would like something working try this:
>
> Slightly modify your data file to be consistent --equal spaces or tabs
>
> x,y = np.loadtxt("data", dtype='float', delimiter=" ", skiprows=1).T
>
> As simple as it gets, the above line successfully loads the data.
>
> Give it a try...
>
>>
>> Manuel
>>
>>
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>
>
>
> --
> Gökhan
>
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