Specify axis-data margin in matplotlib

Question

I have a series of plots with categorical data on the y-axis. It seems that the additional margin between the axis and the data is correlated with the number of categories on the y-axis. If there are many categories, an additional margin appears, but if there are few, the margin is so small that the data points are being cut. The plots look like this:

The plot with few categories and too small margin:

The plot with many categories and too big margins (click for full size):

For now, I only found solutions to manipulate the white space around the plot, like bbox_inches='tight' or fig.tight_layout(), but this doesn't solve my problem. I don't have such problems with the x-axis, can this be a question of x-axis containing only numerical values and y-axis categorical data?

The code I'm using to generate all the plots looks like this:

sns.set(style='whitegrid')
plt.xlim(left=left_lim, right=right_lim)
plt.xticks(np.arange(left_lim, right_lim, step))
plot = sns.scatterplot(method.loc[:,'Len'], 
                       method.loc[:,'Bond'],
                       hue = method.loc[:,'temp'],
                       palette= palette,
                       legend = False, 
                       s = 50)

set_size(width, height)
plt.savefig("method.png", dpi = 100, bbox_inches='tight', pad_inches=0)
plt.show()

The set_size() comes from the first answer to Axes class - set explicitly size (width/height) of axes in given units.

The margin is always 5% on each side. This means that there is more space in absolute units the larger the figure. A solution how to use the same margin would hence depend on how you determine the figure size. (This question contains no code!) — ImportanceOfBeingErnest, Jan 14 '20 at 17:11

score 2 · Accepted Answer · answered Jan 14 '20 at 18:48

We can slightly adapt the function from Axes class - set explicitly size (width/height) of axes in given units to add a line setting the axes margins.

import matplotlib.pyplot as plt

def set_size(w,h, ax=None, marg=(0.1, 0.1)):
    """ w, h: width, height in inches """
    if not ax: ax=plt.gca()
    l = ax.figure.subplotpars.left
    r = ax.figure.subplotpars.right
    t = ax.figure.subplotpars.top
    b = ax.figure.subplotpars.bottom
    figw = float(w)/(r-l)
    figh = float(h)/(t-b)
    ax.figure.set_size_inches(figw, figh)
    ax.margins(x=marg[0]/w, y=marg[1]/h)

And call it with

set_size(width, height, marg=(xmargin, ymargin))

where xmargin, ymargin are the margins in inches.

Specify axis-data margin in matplotlib

1 Answers1