Matplotlib Errorbars Weirdness

Some time ago, I was having trouble with using error bars with a legend in matplotlib. I did some hack to fix it that time.
Today, I came across the same issue again at the scikit-learn sprint.
Obviously this time we wanted to do it right^TM.

The problem is that when doing a plot with error bars, the colors in the legend don't correspond to the colors of the lines.

The problem seems to be solved in never versions, though.

After fiddling a bit with it I found the problem:
The errorbars command actually returns a list of artists, corresponding to the lines AND the individual error bars. That seems to really confuse the legend.

You can solve the problem by doing
errorbar  = pl.errorbars(x, y, err)
line = errorbar[0]
legend(line, 'the line')
taking the zeroth element of the tuple extracts just the line from the collection of
artists and everything works out :)

Comments

  1. Thanks, was driving me mad! My legend wasn't displaying the correct markers and lines after the initial one, this sorted it.

    ReplyDelete
  2. It was driving me crazy, too. Glad I could help you with it.

    ReplyDelete

Post a Comment

Popular posts from this blog

Machine Learning Cheat Sheet (for scikit-learn)

A Wordcloud in Python

MNIST for ever....

Don't cite the No Free Lunch Theorem