Matplotlib Text Alignment in Table

Question

I am struggling to left/right align text properly without having wasted space in the columns. The same col widths are being used for center/left/right:

Center aligned: properly centered, ok
Left aligned: wasted space on the left
Even with omitting colWidths as table argument and playing around with my favorite solution the_table._autoColumns = range (-1,len (colLabels)) does not improve the situation

What am I doing wrong? Is this a bug in matplotlib?

Best Regards, René

import pandas as pd 
import matplotlib.pyplot as plt

size_x, size_y = 12, 4
fig = plt.figure (figsize=(size_x, size_y))
ax  = fig.add_subplot(111)

col_ID    = pd.Series ([ "R001", "R002", "R003", "R005", "R006", "R007" ])
col_Title = pd.Series ([ 50*"*", 10*"-", 70*"x", "R005", "R006", "R007" ])
col_x     = pd.Series ([  3,      1,      3,      4,      2,      3 ])
col_y     = pd.Series ([  4,      2,      3,      2,      4,      3 ])

legend_df = pd.DataFrame ({ "ID"    : col_ID,
                            "Title" : col_Title,
                            "X-Pos" : col_x,
                            "Y-Pos" : col_y,
                            "Value" : col_x * col_y })
rowLabels = legend_df.index
colLabels = legend_df.columns
cellText  = legend_df.values

# Center-Aligned text looks ok
the_table = plt.table (cellText=cellText, rowLabels=rowLabels, colLabels=colLabels, loc='upper center', cellLoc="center", colWidths=[0.05, 0.52, 0.05, 0.05, 0.05, 0.05])

# Bogus: Same colWidths, but left OR right aligned -> unwanted space in title column
# the_table = ax.table (cellText=cellText, rowLabels=rowLabels, colLabels=colLabels, loc='upper center', cellLoc="left", colWidths=[0.05, 0.52, 0.05, 0.05, 0.05, 0.05])

the_table.auto_set_font_size(False)
the_table.set_fontsize (8)

# Set col width automatically
# the_table._autoColumns = range (-1,len (colLabels))

ax.xaxis.set_visible (False)                                            # Grafik-Achsen ausschalten, wir wollen nur Plot
ax.yaxis.set_visible (False)
# the_table.scale(2, 2) 

plt.show()

ImportanceOfBeingErnest · Accepted Answer · 2019-07-09 14:34:23Z

4

Per default the cells have a 10% padding to both sides, which is useful to let the text start a bit next to the table cell border. For very large cells 10% is then too much and leads to the undesired large space.

To overcome this, one would need to set the padding for the column in question to a lower value, as for all other columns 10% is actually desireable. There is no built-in option to set the padding, but one may manipulate it by looping over the cells of the column and changing the respective PAD attribute.

def set_pad_for_column(col, pad=0.1):
    cells = the_table.get_celld()
    column = [cell for cell in the_table.get_celld() if cell[1] == col]
    for cell in column:
        cells[cell].PAD = pad

set_pad_for_column(col=1, pad=0.01)

This produces a padding of 1% only for the second column (col=1).

edited Jul 9, 2019 at 14:34

answered Jun 28, 2017 at 9:46

ImportanceOfBeingErnest

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5 Comments

René Over a year ago

Thanks for the quick response. Wouldn't it be better to have the padding value depend on the font size rather than the column width?

ImportanceOfBeingErnest Over a year ago

The way the table class is written in matplotlib, there is no way to change the padding to be font-size dependent - apart of course from subclassing the table class and the cell class and reimplementing the respective method. Are you asking my opinion on this design choice?

René Over a year ago

Maybe it is worth to open a bug in matplotlib? From my point of view a work around exists (your solution) but sane defaults/algorithms should exist so users do not have to tweak implementation internals - what is your opinion?

ImportanceOfBeingErnest Over a year ago

This is your choice. I would not call it bug-report but feature-request, but you can file that at the matplotlib issue page. Personally I would not consider this to be very urgent or necessary, but that's only my point of view, others may see it differently.

René Over a year ago

New issue created

Clapham · Accepted Answer · 2019-07-09 14:56:44Z

3

Equivalent to answer by ImportanceOfBeingErnest but with a shorter syntax (not as function):

 for key,cell in the_table.get_celld().items():
    if key[1]==1:                   
        cell.PAD = 0.01

The code gets the second column of the_table and changes the padding.

answered Jul 9, 2019 at 14:56

Clapham

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