从分组的条形图中删除空条

Question

I have a grouped barplot. It's working very well, but I try to remove the empty barplots. They take too much space.

I have already tried :

%matplotlib inline
import matplotlib as mpl
from matplotlib.gridspec import GridSpec
import matplotlib.pyplot as plt
import sys
import os
import glob
import seaborn as sns
import pandas as pd
import ggplot
from ggplot import aes

sns.set(style= "whitegrid", palette="pastel", color_codes=True )

tab_folder = 'myData'
out_folder ='myData/plots'
tab = glob.glob('%s/R*.tab'%(tab_folder))

#is reading all my data
for i, tab_file in enumerate(tab):
    folder,file_name=os.path.split(tab_file)
    s_id=file_name[:-4].replace('DD','')
    df=pd.DataFrame.from_csv(tab_file, sep='\t')

    df_2 = df.groupby(['name','ab']).size().reset_index(name='count')

    df_2 = df_2[df_2['count'] != 0]

    table = pd.pivot_table(df_2, index='name',columns='ab', values='count' ) 
    table.plot(kind='barh', width = 0.9, color = ['b', 'g', 'r'], ax = ax)

    for label in (ax.get_xticklabels() + ax.get_yticklabels()):

        label.set_fontsize(4)


    ax.set_title(s_id).update({'color':'black', 'size':5, 'family':'monospace'})
    ax.set_xlabel('')
    ax.set_ylabel('')

    handles, labels = ax.get_legend_handles_labels()
    ax.legend(handles[::-1], labels[::-1], bbox_to_anchor=(1, 1.05),prop= {'size': 4} )

png_t = '%s/%s.b.png'%(out_folder,s_id)
plt.savefig(png_t, dpi = 500)

But it's not working. The bars are still the same. Is there any other method to remove empty bars?

Answer 1

Your question is not complete. I don't know what you're trying to accomplish, but from what you've said I'd guess that you are trying not to display empty pivot pairs.

This is not possible by standard means of pandas. Plot of groups need to display all of them even NaNs which will be plot as "empty bars" .

Furthermore after groupby every group is at least size of one, so df_2[df_2['count'] != 0] is allways true.

For example

df = pd.DataFrame([['nameA', 'abA'], ['nameB', 'abA'],['nameA','abB'],['nameD', 'abD']], columns=['names', 'ab'])
df_2 = df.groupby(['names', 'ab']).size().reset_index(name='count')
df_2 = df_2[df_2['count'] != 0] # this line has no effect
table = pd.pivot_table(df_2, index='names',columns='ab', values='count' ) 
table

gives

ab      abA     abB     abD
names           
nameA   1.00    1.00    NaN
nameB   1.00    NaN     NaN
nameD   NaN     NaN     1.00

and

table.plot(kind='barh', width = 0.9, color = ['b', 'g', 'r'])

shows

And that's the way it is. Plot need to show all groups after pivot.

EDIT

You can also use stacked plot, to get rid of spaces

table.plot(kind='barh', width = 0.9, color = ['b', 'g', 'r'], stacked=True)