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pythonmatplotlibplotspacingsuptitle

Python, Matplotlib: Suptitle with arbitrary number of vertical figures

I have a website that produces (depending on available data stations running) an arbitrary number of plots (as an image), that are vertically stacked over one another. An example is the following:

enter image description here

The problem is that depending on the number of vertical plots, the suptitle (top title) goes to a different position. Check the following examples of 5 and 10 plots:

5 plots:

enter image description here

And here's 10 plots:

enter image description here

So for every number of plots, I get a different result. Using fig.tight_layout() didn't help.

What I need is to have the bottom of my text at a certain distance from the top of the plots. Is there a general answer to this problem?

I created some minimal working code that has the number of plots parametrized. Please check it out if you would like to reproduce this problem.

import datetime
import random
import matplotlib
matplotlib.use('Agg') # Force matplotlib not to use any Xwindows backend.

import matplotlib.pyplot as plt
import matplotlib.dates as mdates
import matplotlib.image as mpimg
import matplotlib.gridspec as gridspec
import numpy as np


random.seed(datetime.datetime.now())

#initial parameters
numOfPlots  = 2
dataLen     = 100
randomRange = 10*dataLen
dpiVal      = 180

#create data
xData = list(range(dataLen) for x in range(numOfPlots))
yData = list(random.sample(range(randomRange), dataLen) for x in range(numOfPlots))

#matplotlib initialize plot
gs = gridspec.GridSpec(numOfPlots,1)
plt.cla()
plt.clf()
fig = plt.figure()
ax = None

for i in list(range(numOfPlots)):
    if i == 0:
        ax = fig.add_subplot(gs[i])
    else:
        ax = fig.add_subplot(gs[i],sharex=ax)

    ax.plot(xData[i], yData[i])

    labelSize = 10
    ax.set_ylabel("Hi there",size=8)
    ax.get_yaxis().set_label_coords(-0.07,0.5)
    plt.yticks(size=8)
    plt.ticklabel_format(style='sci', axis='y', scilimits=(0,0),useOffset=True)
    plt.subplots_adjust(hspace = 0.3)
    if i == numOfPlots-1:
        plt.xticks(rotation=0,size=7)
        max_xticks = 10
        xloc = plt.MaxNLocator(max_xticks)
        ax.xaxis.set_major_locator(xloc)
        ax=plt.gca()
    else:
        plt.tick_params(
        axis='x',          # changes apply to the x-axis
        labelbottom='off') # labels along the bottom edge are off
    ax_right = ax.twinx()
    ax_right.yaxis.set_ticks_position('right')
    ax_right.set_ylabel("Nice to see you!",size=labelSize)
    ax_right.get_yaxis().set_ticks([])


#the following sets the size and the aspect ratio of the plot
fig.set_size_inches(10, 1.8*numOfPlots)

fig.suptitle("Hi there, this is the first line\nAnd this is the second!!!")
fig.savefig("img_"+str(numOfPlots)+".png",bbox_inches='tight',dpi=dpiVal)
Solution

  • I suggest trying something manual: adding text annotation with position in units of the figure relative coordinates.

    Consider these two dummy examples:

    hf,ax = plt.subplots(nrows=3)
hf.text(0.5,0.92,
        "Hi there, this is the first line\nAnd this is the second!!!",
        horizontalalignment='center')
hf,ax = plt.subplots(nrows=7)
hf.text(0.5,0.92,
        "Hi there, this is the first line\nAnd this is the second!!!",
        horizontalalignment='center')

    The result has the "suptitle" located in the exact same position:

    case1 case2