how to resize figures within a subplot using matplotlib

Question

I'm trying to resize two figures within a subplot. Basically, I want a subplot with a temperature profile at 111 and a pressure profile at 211. However, I want the pressure figure to be smaller than the temperature figure. is this possible without the rather complicated gridspec lib? I have the following code:

import pandas as pd
import matplotlib.pyplot as plt
import numpy as np

# ------Pressure------#

df1 = pd.DataFrame.from_csv('Pressure1.csv',index_col = None)
df1['P'] = df1['P'].str.split('.').str[:-1].str.join(',').str.replace(',', '.').astype(np.float64)
a = df1['T']
a /= 2900 # Convert milliseconds to hours
initial_time = 0
a += initial_time - min(a)
b = df1['P']
b -=+1 #convert from volts to bar

# ------- Temperature----------#

df = pd.DataFrame.from_csv('Temperature1.csv',index_col = None)

w = df['Time']
w /= 3600000 # Convert milliseconds to hours
initial_time = 0
w += initial_time - min(w)

x = df['Input 1']
y = df['Input 2']
z = df['Input 3']

#----subplot----#

plt.subplot(1,1,1)
figsize(20,10)
plt.plot(w,x, label = "Top_sensor")
plt.plot(w,y, label = "Mid_sensor")
plt.plot(w,z, label = 'Bot_sensor')
plt.title('Temperature')
plt.xlabel('Time(Hours)')
plt.ylabel('Temperature (K)')
plt.ylim(70, 200)
plt.xlim(0, 12, 1)
plt.show()

plt.subplot(2,1,1)
figsize(20,3)
plt.plot(a,b)
plt.title('Pressure_Monitoring')
plt.xlabel('Time(Hours)')
plt.ylabel('Pressure (Bar)')
plt.xlim(0, 12, 1)
plt.show()

See how I try to change the figsize in each subplot. Is this the wrong way?

Okay, so i've managed to get the gridspec i want. But, how do i combine the two?

import matplotlib.gridspec as gridspec

f = plt.figure()

gs = gridspec.GridSpec(2, 1,width_ratios=[20,10], height_ratios=[10,5])

ax1 = plt.subplot(gs[0])
ax2 = plt.subplot(gs[1])

plt.show()

Try ax1 = plt.subplot(gs[0, :]) and ax2 = plt.subplot(gs[1, :]). — alacy
– alacy, Commented Feb 2, 2015 at 14:25

pkout · Accepted Answer · 2017-11-26 03:59:16Z

4

This is why the pyplot interface is so bad. This is way more complicated than it needs to be.

Load and prepare your data. Then:

fig = plt.Figure(figsize=(20, 3))
gs = gridspec.GridSpec(2, 1, width_ratios=[20,10], height_ratios=[10,5])
ax1 = fig.add_subplot(gs[0])
ax2 = fig.add_subplot(gs[1])

ax1.plot(...)
ax1.set_ylabel(...)
...

ax2.plot(...)
ax2.set_xlabel(...)

That way, you don't have to create any extraneous objects that don't really get used and it's always explicit as to which axes is being modified.

edited Nov 26, 2017 at 3:59

pkout

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answered Feb 2, 2015 at 16:20

Paul H

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1 Comment

Adriaan Over a year ago

A much nicer interface than pyplot indeed! However, when I tried to run the code above I got two errors. 1) plt.Figure should be lower case plt.figure 2) for a 2x1 grid, the width should be defined as a single value list since there is only one width to set, so width_ratios=[20].

alacy · Accepted Answer · 2015-02-02 14:45:41Z

2

Try:

ax1 = plt.subplot(gs[0, :])
ax2 = plt.subplot(gs[1, :])

and then set your axes like so:

plt.axes(ax1)

answered Feb 2, 2015 at 14:45

alacy

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3 Comments

Paul H Over a year ago

wouldn't it just be better to actually plot against the ax1 and ax2? (i.e., ax.plot(...)

alacy Over a year ago

@PaulH yes, I would agree with you. I also agree with what you stated in your response that pyplot does not provide a very good interface which causes an overcomplicating of simple plots and inserts too much ambiguity on how to configure that same simple plot.

tacaswell Over a year ago

As @PaulH says, this is the case where the OO interface is much easier to use. While this isn't wrong I am tempted to down vote because it is bad practice.

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