Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Welcome To Ask or Share your Answers For Others

Categories

0 votes
353 views
in Technique[技术] by (71.8m points)

python - How to select rows in Pandas dataframe where value appears more than once

Let's say I have the Pandas dataframe with columns of different measurement attributes and corresponding measurement values.

ID     Parameter     Value
0      'A'           4.3
1      'B'           3.1
2      'C'           8.9
3      'A'           2.1
4      'A'           3.9
.      .             .
.      .             .
.      .             .
100    'B'           3.8

How can I filter this dataframe to only have measurements that appear more than X number of times? For example, for this dataframe I want to get all rows with more than 5 measurements (lets say only parameters 'A' and 'B' appear more than 5 times) to get a dataframe like below.

ID     Parameter     Value
0      'A'           4.3
1      'B'           3.1
3      'A'           2.1
.      .             .
.      .             .
.      .             .
100    'B'           3.8
See Question&Answers more detail:os

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
Welcome To Ask or Share your Answers For Others

1 Reply

0 votes
by (71.8m points)

You can use value_counts + isin -

v = df.Parameter.value_counts()
df[df.Parameter.isin(v.index[v.gt(5)])]

For example, where K = 2 (get all items which have more than 2 readings) -

df

   ID Parameter  Value
0   0         A    4.3
1   1         B    3.1
2   2         C    8.9
3   3         A    2.1
4   4         A    3.9
5   5         B    4.5

v = df.Parameter.value_counts()
v

A    3
B    2
C    1
Name: Parameter, dtype: int64

df[df.Parameter.isin(v.index[v.gt(2)])]

   ID Parameter  Value
0   0         A    4.3
3   3         A    2.1
4   4         A    3.9

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
OGeek|极客中国-欢迎来到极客的世界,一个免费开放的程序员编程交流平台!开放,进步,分享!让技术改变生活,让极客改变未来! Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Click Here to Ask a Question

...