CODEWITHSUNDEEP
pythonmatplotlib
zephyr
zephyr

Reputation: 2332

Pyplot set tick frequency and tick labels

I'm trying to make a plot with matplotlib where I want to specify both the position of the tick marks, and the text of the tick marks. I can individually do both with yticks(np.arange(0,1.1,1/16.)) and gca().set_yticklabels(['1','2','3']). However, for some reason when I do both of them together, the labels do not appear on the graph. Is there a reason for this? How can I get around it? Below is a working example of what I want to accomplish.

x = [-1, -0.2, -0.15, 0.15, 0.2, 7.8, 7.85, 8.15, 8.2, 12]
y = [1, 1, 15/16., 15/16., 1, 1, 15/16., 15/16., 1, 1]

figure(1)
plot(x,y)
xlabel('Time (years)')
ylabel('Brightness')
yticks(np.arange(0,1.1,1/16.))
xticks(np.arange(0,13,2))
ylim(12/16.,16.5/16.)
xlim(-1,12)
gca().set_yticklabels(['12/16', '13/16', '14/16', '15/16', '16/16'])
show(block = False)

Effectively I just wanted to replace the numerical values with fractions, but when I run this, the labels do not appear. It seems that using both yticks() and set_yticklabels together is a problem because if I remove either line, the remaining line works as it should.

If anyone can indicate how to simply force the label to be a fraction, that would also solve my problem.

EDIT: I found an ugly workaround by using

ylim(12/16., 16.5/16)
gca().yaxis.set_major_locator(FixedLocator([12/16., 13/16., 14/16., 15/16., 16/16.]))
gca().yaxis.set_major_formatter(FixedFormatter(['12/16', '13/16', '14/16', '15/16', '16/16']))

While this may work for this specific example, it does not generalize well and it is cumbersome to specify the exact location and label of every tick mark. If anyone finds another solution, I'm all ears.

Upvotes: 1

Views: 11176

Answers (1)

joaquin
joaquin

Reputation: 85633

1) Your arange should produce 5 ticks, the same as labels you set.
arange is not good for that. It is better to use linspace.

2) You can set ticks and labels with the same function

plot(x,y)
xlabel('Time (years)')
ylabel('Brightness')
yticks(np.linspace(12/16., 1, 5), ('12/16', '13/16', '14/16', '15/16', '16/16') )
xticks(np.arange(0,13,2))
ylim(12/16.,16.5/16.)
xlim(-1,12)

enter image description here

3) Note that you should adjust the actual values of the axis with the position of the labels using linspace(12/16., 1, 5) instead of arange(0, 1.1, 1/16.))

Upvotes: 2

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