Plot number of occurrences from Pandas DataFrame

Question

I have a DataFrame with two columns. One of them is containing timestamps and another one - id of some action. Something like that:

2000-12-29 00:10:00     a         


        

Answer 1

You can get the counts by using

df.groupby([df.index.date, 'action']).count()

or you can plot directly using this method

df.groupby([df.index.date, 'action']).count().plot(kind='bar')

You could also just store the results to count and then plot it separately. This is assuming that your index is already in datetimeindex format, otherwise follow the directions of @mkln above.

Answer 2

Starting from

                mydate col_name
0  2000-12-29 00:10:00  action1
1  2000-12-29 00:20:00  action2
2  2000-12-29 00:30:00  action2
3  2000-12-29 00:40:00  action1
4  2000-12-29 00:50:00  action1
5  2000-12-31 00:10:00  action1
6  2000-12-31 00:20:00  action2
7  2000-12-31 00:30:00  action2

You can do

df['mydate'] = pd.to_datetime(df['mydate'])
df = df.set_index('mydate')
df['day'] = df.index.date
counts = df.groupby(['day', 'col_name']).agg(len)

but perhaps there's an even more straightforward way. the above should work anyway.

If you want to use counts as a DataFrame, I'd then transform it back

counts = pd.DataFrame(counts, columns=['count'])