Matplotlib: how to set only min and max values for tics

Question

I have pretty similar code to plot:

plt.plot(df_tags[df_tags.detailed_tag == tag]['week'], df_tags[df_tags.detailed_tag == tag].tonality)

Output:

But I want leave only min and max values for x axis this way:

plt.plot(df_tags[df_tags.detailed_tag == tag]['week'], df_tags[df_tags.detailed_tag == tag].tonality)
plt.xticks([df_tags['week'].min(), df_tags['week'].max()])
print (df_tags['week'].min(), df_tags['week'].max())

With no luck, he puts second week as a last one, but why and how to fix it:

Can you please include your small data frame, so people can use it for their tests? — Mr. T, Mar 02 '18 at 09:18

ImportanceOfBeingErnest · Accepted Answer · 2018-03-05T10:40:53.077

This can't be answered with certainty due to the unknown input data. Interpreting the small amount of code that is shown one would go for setting the ticks and labels,

t = [df_tags['week'].min(), df_tags['week'].max()]
plt.xticks(t,t)

To explain why plt.xticks(t) alone does not work:
The inital plot's axis has some tick locations and ticklabels set, i.e. tick locations corresponding to [2018-03, 2018-04, 2018-05,...] and the respective ticklabels [2018-03, 2018-04, 2018-05,...]. If you now only change the tick locations via plt.xticks([2018-03, 2018-08]), the plot will only have two differing tick locations, but still the same labels to occupy those locations. Hence the second label 2018-04 will occupy the second (and last) position.
Since this is undesired, you should always set the tick positions and the ticklabels. This is done via plt.xticks(ticklocations, ticklabels) or ax.set_xticks(ticklocations); ax.set_xticklabels(ticklabels).

I updated the answer text with some explanation. Hope that helps. — ImportanceOfBeingErnest, Mar 05 '18 at 10:41

score 2 · Answer 2 · answered Mar 02 '18 at 10:34

This hacky solution piggybacks on this SO post

import pandas as pd
import numpy as np

df = pd.DataFrame({'week': ['2018-01', '2018-02', '2018-03', '2018-04', '2018-05', '2018-06', '2018-07', '2018-08'], 'val': np.arange(8)})

fig, ax = plt.subplots(1,1)
ax.plot(df['week'], df['val'])
for i, label in enumerate(ax.get_xticklabels()):
    if i > 0 and i < len(ax.get_xticklabels()) - 1:
        label.set_visible(False)
plt.show()

Matplotlib: how to set only min and max values for tics

2 Answers2