Cannot change default colormap in matplotlib

Question

I am trying to set the default colormap (not just the color of a specific plot) for matplotlib in my jupyter notebook (Python 3). I found the commands: plt.set_cmap("gray") and mpl.rc('image', cmap='gray'), that should set the default colormap to gray, but both commands are just ignored during execution and I still get the old colormap.

I tried these two codes:

import matplotlib as mpl
mpl.rc('image', cmap='gray')
plt.hist([[1,2,3],[4,5,6]])

import matplotlib.pyplot as plt
plt.set_cmap("gray")
plt.hist([[1,2,3],[4,5,6]])

They should both generate a plot with gray tones. However, the histogram has colors, which correspond to the first two colors of the default colormap. What am I not getting?

Thanks! But in your link it's not the default behaviour. But it did tell me that what I need to change is not the colormap but the color cycle. When you get this, then the answer is here: stackoverflow.com/questions/9397944/… — Fringant
– Fringant, Commented Sep 13, 2019 at 15:22

Fringant · Accepted Answer · 2019-09-13 15:18:25Z

1

Thanks to the comment of Chris, I found the issue, it's not the default colormap that I need to change but the default color cycle. it's described here: How to set the default color cycle for all subplots with matplotlib?

import matplotlib as mpl
import matplotlib.pyplot as plt
from cycler import cycler

# Set the default color cycle
colors=plt.cm.gray(np.linspace(0,1,3))
mpl.rcParams['axes.prop_cycle'] = mpl.cycler(color=colors)
plt.hist([[1,2,3],[4,5,6]])

answered Sep 13, 2019 at 15:18

Fringant

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Comments

Chris · Accepted Answer · 2019-09-13 13:43:49Z

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Since you have two data sets your are passing, you'll need to specify two colors.

plt.hist([[1,2,3],[4,5,6]], color=['black','purple'])

answered Sep 13, 2019 at 13:43

Chris

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1 Comment

Fringant Over a year ago

I need to change the color map in the whole notebook. Not just for one plot.

stephen_mugisha · Accepted Answer · 2019-09-13 13:52:31Z

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You can make use of the color argument in matplotlib plot function.

import matplotlib.pyplot as plt
plt.hist([[1,2,3],[4,5,6]], color=['gray','gray'])

with this method you have to specify the color scheme for each dataset hence an array of colors as I have put it above.

edited Sep 13, 2019 at 13:52

answered Sep 13, 2019 at 13:40

stephen_mugisha

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1 Comment

Fringant Over a year ago

I need to change the color map in the whole notebook. Not just for one plot.

Massifox · Accepted Answer · 2019-09-13 14:03:01Z

0

If you are using a version of matplotlib between prio and 2.0 you need to use rcParams (still working in newer versions):

import matplotlib.pyplot as plt

plt.rcParams['image.cmap'] = 'gray'

edited Sep 13, 2019 at 14:03

Massifox

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answered Sep 13, 2019 at 13:42

Paul Legrand

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1 Comment

Fringant Over a year ago

Same problem. Default colormap unchanged. Does the code work for you? I'm using python 3.0 and jupyter notebook.

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