loadtxt/usecols -> list index out of range

Manuel_Wittchen · November 16, 2009, 10:34pm

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?

Manuel

_Ryan_May1 · November 16, 2009, 10:49pm

Check your data file. What you posted to the list is copy/pasting as
8 spaces for me, but you are specifying delimiter='\t'. I'd try just
not specifying delimiter or passing in delimiter=None.

Ryan

···

On Mon, Nov 16, 2009 at 4:34 PM, Manuel Wittchen <manuel.wittchen@...287...> 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?

--
Ryan May
Graduate Research Assistant
School of Meteorology
University of Oklahoma

Gokhan_SEVER1 · November 16, 2009, 10:53pm

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
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…

···

On Mon, Nov 16, 2009 at 4:34 PM, Manuel Wittchen <manuel.wittchen@…287…> wrote:

Manuel

Let Crystal Reports handle the reporting - Free Crystal Reports 2008 30-Day

trial. Simplify your report design, integration and deployment - and focus on

what you do best, core application coding. Discover what’s new with

Crystal Reports now. http://p.sf.net/sfu/bobj-july

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–
Gökhan

Manuel_Wittchen · November 16, 2009, 11:37pm

********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 <gokhansever@...287...>:

···

On Mon, Nov 16, 2009 at 4:34 PM, Manuel Wittchen <manuel.wittchen@...985.....> > 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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30-Day
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--
Gökhan