matplotlib get ylim values

Question

I'm using matplotlib to plot data (using plot and errorbar functions) from Python. I have to plot a set of totally separate and independent plots, and then adjust their ylim values so they can be easily visually compared.

How can I retrieve the ylim values from each plot, so that I can take the min and max of the lower and upper ylim values, respectively, and adjust the plots so they can be visually compared?

Of course, I could just analyze the data and come up with my own custom ylim values... but I'd like to use matplotlib to do that for me. Any suggestions on how to easily (and efficiently) do this?

Here's my Python function that plots using matplotlib:

import matplotlib.pyplot as plt

def myplotfunction(title, values, errors, plot_file_name):

    # plot errorbars
    indices = range(0, len(values))
    fig = plt.figure()
    plt.errorbar(tuple(indices), tuple(values), tuple(errors), marker='.')

    # axes
    axes = plt.gca()
    axes.set_xlim([-0.5, len(values) - 0.5])
    axes.set_xlabel('My x-axis title')
    axes.set_ylabel('My y-axis title')

    # title
    plt.title(title)

    # save as file
    plt.savefig(plot_file_name)

    # close figure
    plt.close(fig)

PatrickT · Accepted Answer · 2024-09-04 19:17:11Z

266

Just use axes.get_ylim(), it is very similar to set_ylim. From the docs:

get_ylim()

Get the y-axis range [bottom, top]

edited Sep 4, 2024 at 19:17

PatrickT

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answered Sep 30, 2014 at 23:12

elyase

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5 Comments

Peter Ehrlich Over a year ago

is there a way to get the graph area limit, rather than the axis limit? The black bounding rectangle is slightly beyond these values.

ilija139 Over a year ago

@PeterEhrlich That's just the margins.

Matthias Arras Over a year ago

I find plt.gca().get_ylim() to be handy - no need for extra axes definition.

BallpointBen Over a year ago

Alternatively, I prefer to use fig, ax = plt.subplots() and then route all my functions through either fig or ax

Simon Chemnitz-Thomsen Over a year ago

I had to use fig.axes[0].get_ylim(), plt.gca().get_ylim() just returns (0.0, 1.0)

Adam Hughes · Accepted Answer · 2021-02-22 14:31:31Z

58

 ymin, ymax = axes.get_ylim()

If you are using the plt api directly, you can avoid calls to axes altogether:

def myplotfunction(title, values, errors, plot_file_name):

    # plot errorbars
    indices = range(0, len(values))
    fig = plt.figure()
    plt.errorbar(tuple(indices), tuple(values), tuple(errors), marker='.')

    plt.ylim([-0.5, len(values) - 0.5])
    plt.xlabel('My x-axis title')
    plt.ylabel('My y-axis title')

    # title
    plt.title(title)

    # save as file
    plt.savefig(plot_file_name)

   # close figure
    plt.close(fig)

edited Feb 22, 2021 at 14:31

answered Sep 30, 2014 at 23:17

Adam Hughes

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3 Comments

BigHeadEd Over a year ago

Are there advantages to using the plt api directly vs using axes? I see numerous people suggest that using axes is better, but I haven't been able to nail down why.

Adam Hughes Over a year ago

Axes is more programatic - so for example you can build a library of functions that take and operate on axes objects. But the plt object is more for just doing something quick. So if you're tinkering, plt is faster. If you're building a bigger app, axes probably best. This has been my experience anyway. It's overall a weird API to be honest.

hintze Over a year ago

The overall weird API has its roots in MATLAB. Source: matplotlib.org/stable/users/history.html

Thom Ives · Accepted Answer · 2019-07-31 19:27:09Z

Leveraging from the good answers above and assuming you were only using plt as in

import matplotlib.pyplot as plt

then you can get all four plot limits using plt.axis() as in the following example.

import matplotlib.pyplot as plt

x = [1, 2, 3, 4, 5, 6, 7, 8]  # fake data
y = [1, 2, 3, 4, 3, 2, 5, 6]

plt.plot(x, y, 'k')

xmin, xmax, ymin, ymax = plt.axis()

s = 'xmin = ' + str(round(xmin, 2)) + ', ' + \
    'xmax = ' + str(xmax) + '\n' + \
    'ymin = ' + str(ymin) + ', ' + \
    'ymax = ' + str(ymax) + ' '

plt.annotate(s, (1, 5))

plt.show()

The above code should produce the following output plot.

Gabriel Cia · Accepted Answer · 2021-11-11 13:27:24Z

9

Just use plt.ylim(), it can be used to set or get the min and max limit

ymin, ymax = plt.ylim()

answered Nov 11, 2021 at 13:27

Gabriel Cia

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1 Comment

sol Over a year ago

Warning: if you use axes, this solution will always return ymin=0, ymax=1. Prefer in this case ymin, ymax = axes.get_ylim()

aVral · Accepted Answer · 2023-09-02 09:56:16Z

4

Wihout defining axes:

min_lim, max_lim = plt.xlim()

answered Sep 2, 2023 at 9:56

aVral

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Comments

Jiadong · Accepted Answer · 2020-10-13 02:10:22Z

3

I put above-mentioned methods together using ax instead of plt

import numpy as np
import matplotlib.pyplot as plt

x = range(100)
y = x

fig, ax = plt.subplots(1, 1, figsize=(7.2, 7.2))
ax.plot(x, y);

# method 1
print(ax.get_xlim())
print(ax.get_xlim())
# method 2
print(ax.axis())

answered Oct 13, 2020 at 2:10

Jiadong

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Comments

Jim · Accepted Answer · 2020-10-06 19:47:43Z

0

It's an old question, but I don't see mentioned that, depending on the details, the sharey option may be able to do all of this for you, instead of digging up axis limits, margins, etc. There's a demo in the docs that shows how to use sharex, but the same can be done with y-axes.

answered Oct 6, 2020 at 19:47

Jim

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