How to set title to sublots from a list in matplotlib

Question

I try to set title for subplots from array of data.

What I expect to have is that Title-1, Title-2 ... and so on for (00, 01 , 10 and 11) locations in the figure.

So I did;

import matplotlib.pyplot as plt    

title = [1,2,3,4]

fig, ax = plt.subplots(2, 2, figsize=(6, 8))  

    for i in range(len(ax)): 
        for j in range(len(ax[i])):

            for k in title:
            #    print (k)
                ax[i,j].set_title('Title-' + str(k))

But only getting Title-4. How can I fix this issue ? Thx

@sshashank124 No the link does not answer to my question! I have array of data to feed the title. — Alexander, Dec 29 '19 at 05:34

score 5 · Accepted Answer · answered Dec 29 '19 at 06:06

One method use flatten and enumerate:

import matplotlib.pyplot as plt    

title = [1,2,3,4]

fig, ax = plt.subplots(2, 2, figsize=(6, 8))  
flat_ax = ax.flatten()

for n, ax in enumerate(flat_ax):
    ax.set_title(f'Title-{title[n]}')

Output:

Another option is to use iter with flatten:

import matplotlib.pyplot as plt    

title = [1,2,3,4]
ititle = iter(title)

fig, ax = plt.subplots(2, 2, figsize=(6, 8))  
flat_ax = ax.flatten()

for ax in flat_ax:
    ax.set_title(f'Title-{next(ititle)}')

Also, note I am using f-string which requires python 3.6+

score 2 · Answer 2 · answered Dec 29 '19 at 06:00

2

This happens because you are doing repeated assignments of title looping from 1 up to 4 for each combination of i, j. You need to refactor your code in a way it does only one assignment for each i and j:

for i in range(len(ax)):
    for j in range(len(ax[i])):
        ax[i,j].set_title('Title-' + str(1+2*i+j))

You might also like to make a dictionary

codes = {(0,0):1, (0,1):2, (1,0):3, (1,1):4}

and replace last line by

ax[i,j].set_title('Title-' + str(codes[i,j]))

answered Dec 29 '19 at 06:00

mathfux

5,759
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Thanks! but What if I have `title = [111,223,1233,423]` type title ? the first solution would not apply! secondly, if I have dozens of titles it becomes a little bit troublesome to create a dictionary for each of them! – Alexander Dec 29 '19 at 06:08
I didn't know there's `flatten` method implemented for this purpose in matplotlib – mathfux Dec 29 '19 at 06:13
1

@mathfux `flatten` is a numpy array method, when you have more than 1 axes defined with `plt.subplots` what is returned is numpy array of axes. – Scott Boston Dec 29 '19 at 06:31

Mykola Zotko · Answer 3 · 2019-12-29T09:40:18.730

1

You can use the function ndindex to iterate over the N-dimensional index of the array:

fig, ax = plt.subplots(2, 2, figsize=(6, 8))
titles = [1,2,3,4]

for idx, t in zip(np.ndindex(ax.shape), titles):
    ax[idx].set_title(f'Title {t}')

edited Dec 29 '19 at 09:40

answered Dec 29 '19 at 09:32

Mykola Zotko

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How to set title to sublots from a list in matplotlib

3 Answers3