CODEWITHSUNDEEP
pythonpython-3.xmatplotlib
Jason
Jason

Reputation: 4546

Using subplot_kw in matplotlib to create a polar projection in subplots

I'm trying to create a polar projection using matplotlib.pyplot.subplots() but I get the error projection is not defined when I try to pass a dictionary to matplotlib.pyplot.subplots()

My code:

import matplotlib.pyplot as plt

fig, ax = plt.subplots(nrows=1, ncols=2, subplot_kw={projection:'polar'})

However plt.subplot(1,1,1, projection='polar') works as expected. The documentation for plt.subplots() says that the dictionary in subplot_kw will be passed to add.subplot() which takes projection as a optional parameter so I'm not sure what my mistake is.

Upvotes: 3

Views: 11058

Answers (2)

Ram HR
Ram HR

Reputation: 1

This is mainly to clarify which was the mistake in the original post and to complete the previous answer.

Following the plt.subplots() documentation you cited, the argument subplot_kw is expected to be dictionary. There are two equivalent ways of doing this.

option 1:
Use the function dict() to create the dictionary to pass:
subplot_kw = dict(projection = 'polar')

oprtion 2:
Pass directly the dictionary in with the correct key-value structure subplot_kw = {'projection' : 'polar'}

Notice that in the first option the word projection does not need to be a string and you can use and equal = sign. The function dict will do the job of formating the dictionary from its arguments. You can verify this simply by doing:

>>>dict(projection = 'polar')
Output: {'projection' : 'polar'}

Upvotes: 0

roganjosh
roganjosh

Reputation: 13185

The docs that you linked don't actually show subplot_kw being used in that way. What they show is calling dict():

fig, axes = plt.subplots(2, 2, subplot_kw=dict(polar=True))

If you print the output of subplot_kw=dict(polar=True), you get:

{'polar': True}

Notice that polar has now become a string. subplot_kw={projection:'polar'}) does not define projection as a string, it's just a variable name that Python now has to look up (and it won't find it in this case, but it may find something else in other cases).

Upvotes: 7

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