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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