Invalid index : Python - matplotlib pyplot

Question

For the following code:

G = [
  [8.29187396e-04,4.98341625e-01,8.29187396e-04,4.98341625e-01,8.29187396e-04,8.29187396e-04],
  [4.99168745e-01,4.15627598e-04,2.49792186e-01,4.15627598e-04,2.49792186e-01,4.15627598e-04],
  [1.66666667e-01,1.66666667e-01,1.66666667e-01,1.66666667e-01,1.66666667e-01,1.66666667e-01],
  [6.65005537e-01,3.32779623e-01,5.53709856e-04,5.53709856e-04,5.53709856e-04,5.53709856e-04],
  [1.66666667e-01,1.66666667e-01,1.66666667e-01,1.66666667e-01,1.66666667e-01,1.66666667e-01],
  [1.65016502e-03,1.65016502e-03,1.65016502e-03,1.65016502e-03,9.91749175e-01,1.65016502e-03],
]

fnames = ['angelinajolie.html', 'bradpitt.html', 'jenniferaniston.html', 
  'jonvoight.html', 'martinscorcese.html', 'robertdeniro.html']

NX = len(fnames)
PI = random(NX)
PI /= sum(PI)

import matplotlib.pyplot as plt
evolution = [numpy.dot (PI, G**i) for i in xrange(1,20)]       

plt.figure()
for i in xrange(NX):
    plt.plot([step[0,i] for step in evolution], label=fnames[i], lw=2 )
    # ^ this line
#plt.draw


    IndexError: invalid index

Im getting this error. Im learning Python and Im not very familiar with the language. Googling this error didnt give any specific solutions. Wondering if someone can help.

Thanks

EDIT:

I tried the following code

import matplotlib.pyplot as plt
evolution = [numpy.dot (PI, G**i) for i in xrange(1,20)]
print 'xrange'
print xrange(1,20)
print ''
print 'evolution = '
print evolution
print ''


for i in xrange (NX):
print (step[0,i] for step in evolution)

And got this output:

xrange
xrange(1, 20)

 evolution = 
 [array([ 0.32804667,  0.21757686,  0.12538595,  0.15799482,  0.12910639,
     0.04188931]), array([ 0.16964679,  0.08472597,  0.02780032,  0.06486529,  0.0314962  ,
     0.00690881]), array([ 0.09553784,  0.03664288,  0.00636997,  0.03003363,   0.01003537,
     0.00115142]), array([ 0.05605324,  0.01678453,  0.00149546,  0.01458511,   0.00513061,
      0.0001919 ]), array([  3.37327444e-02,   7.93664097e-03,   3.57601326e-04,
       7.20471786e-03,   3.96276140e-03,   3.19838999e-05]), array([  2.06957198e-02,      3.82337165e-03,   8.66673387e-05,
       3.57980255e-03,   3.66208187e-03,   5.33064999e-06]), array([  1.29011406e-02,     1.86325141e-03,   2.12057110e-05,
       1.78219658e-03,   3.56712012e-03,   8.88441665e-07]), array([  8.15011563e-03,     9.14821461e-04,   5.22316873e-06,
       8.87848064e-04,   3.52188086e-03,   1.48073611e-07]), array([  5.20576887e-03,     4.51378732e-04,   1.29239804e-06,
       4.42402535e-04,   3.48893476e-03,   2.46789351e-08]), array([  3.35501606e-03,     2.23446508e-04,   3.20779482e-07,
       2.20459413e-04,   3.45918721e-03,   4.11315586e-09]), array([  2.17777263e-03,     1.10856782e-04,   7.97863000e-08,
       1.09862738e-04,   3.43040772e-03,   6.85525976e-10]), array([  1.42161006e-03,     5.50797457e-05,   1.98730096e-08,
       5.47489480e-05,   3.40204477e-03,   1.14254329e-10]), array([  9.32090403e-04,     2.73937246e-05,   4.95462506e-09,
       2.72836418e-05,   3.37396034e-03,   1.90423882e-11]), array([  6.13212265e-04,    1.36332014e-05,   1.23604372e-09,
      1.35965681e-05,   3.34611871e-03,   3.17373137e-12]), array([  4.04478562e-04,    6.78792560e-06,   3.08490244e-10,
      6.77573479e-06,   3.31850955e-03,   5.28955228e-13]), array([  2.67327741e-04,    3.38068736e-06,   7.70144829e-11,
      3.37663051e-06,   3.29112888e-03,   8.81592047e-14]), array([  1.76949431e-04,    1.68406555e-06,   1.92302878e-11,
      1.68271551e-06,   3.26397429e-03,   1.46932008e-14]), array([  1.17260538e-04,    8.39016441e-07,   4.80235424e-12,
      8.38567176e-07,   3.23704380e-03,   2.44886680e-15]), array([  7.77733433e-05,    4.18042435e-07,   1.19938700e-12,
      4.17892928e-07,   3.21033551e-03,   4.08144466e-16])]

     xrange(NX) = 
     xrange(6)
     <generator object <genexpr> at 0x10c1b9f50>
     <generator object <genexpr> at 0x10c1b9f50>
     <generator object <genexpr> at 0x10c1b9f50>
     <generator object <genexpr> at 0x10c1b9f50>
     <generator object <genexpr> at 0x10c1b9f50>
     <generator object <genexpr> at 0x10c1b9f50>

You will need to provide code that shows what evolution and fnames are. — BrenBarn
– BrenBarn, Commented Sep 14, 2012 at 19:05
Try replacing plt.plot call with a print that outputs i and parameters you pass to plt.plot. Run the loop, see if it works. If it does not, you will at least see the value of i when it last worked; it may help you. The example you provided works fine for me with plotting calls removed. — 9000
– 9000, Commented Sep 14, 2012 at 20:11

Martijn Pieters · Accepted Answer · 2012-09-14 19:15:30Z

1

The value of i is too large for either step[0, i] or fnames[i].

In other words, the current value of i is not a valid index into one of those structures. Note that i can be anything between 0 and NX - 1.

You could try and print out the step values first, most likely they do not contain what you expect them to contain.

edited Sep 14, 2012 at 19:15

answered Sep 14, 2012 at 19:09

Martijn Pieters

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2 Comments

banditKing Over a year ago

Oops: added it please see above

9000 Over a year ago

@MartijnPeters: did you try running the code? It worked for me for some reason.

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