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Subset based on most frequent value
Announcing the arrival of Valued Associate #679: Cesar Manara
Planned maintenance scheduled April 23, 2019 at 23:30UTC (7:30pm US/Eastern)
Data science time! April 2019 and salary with experience
The Ask Question Wizard is Live!How do I sort a dictionary by value?Why can't Python parse this JSON data?Peak detection in a 2D arrayHow to access environment variable values?What is the most efficient way to loop through dataframes with pandas?Most elegant way to check if the string is empty in Python?“Large data” work flows using pandasSelect rows from a DataFrame based on values in a column in pandasFillna with most frequent if most frequent occurs else fillna with most frequent value of the entire columnHow to pivot a dataframe
.everyoneloves__top-leaderboard:empty,.everyoneloves__mid-leaderboard:empty,.everyoneloves__bot-mid-leaderboard:empty height:90px;width:728px;box-sizing:border-box;
Say I have the below dataset as a CSV file.
I want my output to be a CSV file which is a subset of this data based on only the data associated with the most frequent value in column B.
In the below example data, the most frequent value in column B is "1", however this will change and so I need my code to not be so specific.
A B
! 1
@ 1
# 1
$ 1
% 2
^ 3
& 2
* 4
( 5
) 2
In this example, I want my output to be a CSV file of:
A B
! 1
@ 1
# 1
$ 1
But since the most frequent value will change, I'm not sure what my code should be.
Any help you can provide will be much appreciated. Thank you.
python pandas pandas-groupby
edited Mar 8 at 22:00
petezurich
3,89081936
asked Mar 8 at 21:44
Amie JohnsonAmie Johnson
254
add a comment |
Say I have the below dataset as a CSV file.
I want my output to be a CSV file which is a subset of this data based on only the data associated with the most frequent value in column B.
In the below example data, the most frequent value in column B is "1", however this will change and so I need my code to not be so specific.
A B
! 1
@ 1
# 1
$ 1
% 2
^ 3
& 2
* 4
( 5
) 2
In this example, I want my output to be a CSV file of:
A B
! 1
@ 1
# 1
$ 1
But since the most frequent value will change, I'm not sure what my code should be.
Any help you can provide will be much appreciated. Thank you.
python pandas pandas-groupby
edited Mar 8 at 22:00
petezurich
3,89081936
asked Mar 8 at 21:44
Amie JohnsonAmie Johnson
254
Welcome to StackOverflow. Just to clarify - if I was to summarise what you are trying to achieve, you would: 1) find most frequent value in B; 2) discard all rows where B is not the most frequent value ?
– 4Oh4
Mar 8 at 22:46
add a comment |
Say I have the below dataset as a CSV file.
I want my output to be a CSV file which is a subset of this data based on only the data associated with the most frequent value in column B.
In the below example data, the most frequent value in column B is "1", however this will change and so I need my code to not be so specific.
A B
! 1
@ 1
# 1
$ 1
% 2
^ 3
& 2
* 4
( 5
) 2
In this example, I want my output to be a CSV file of:
A B
! 1
@ 1
# 1
$ 1
But since the most frequent value will change, I'm not sure what my code should be.
Any help you can provide will be much appreciated. Thank you.
python pandas pandas-groupby
edited Mar 8 at 22:00
petezurich
3,89081936
asked Mar 8 at 21:44
Amie JohnsonAmie Johnson
254
Say I have the below dataset as a CSV file.
I want my output to be a CSV file which is a subset of this data based on only the data associated with the most frequent value in column B.
In the below example data, the most frequent value in column B is "1", however this will change and so I need my code to not be so specific.
A B
! 1
@ 1
# 1
$ 1
% 2
^ 3
& 2
* 4
( 5
) 2
In this example, I want my output to be a CSV file of:
A B
! 1
@ 1
# 1
$ 1
But since the most frequent value will change, I'm not sure what my code should be.
Any help you can provide will be much appreciated. Thank you.
python pandas pandas-groupby
python pandas pandas-groupby
edited Mar 8 at 22:00
petezurich
3,89081936
asked Mar 8 at 21:44
Amie JohnsonAmie Johnson
254
edited Mar 8 at 22:00
petezurich
3,89081936
asked Mar 8 at 21:44
Amie JohnsonAmie Johnson
254
edited Mar 8 at 22:00
petezurich
3,89081936
edited Mar 8 at 22:00
petezurich
3,89081936
edited Mar 8 at 22:00
petezurich
3,89081936
3,89081936
asked Mar 8 at 21:44
Amie JohnsonAmie Johnson
254
asked Mar 8 at 21:44
Amie JohnsonAmie Johnson
254
asked Mar 8 at 21:44
Amie JohnsonAmie Johnson
254
254
Welcome to StackOverflow. Just to clarify - if I was to summarise what you are trying to achieve, you would: 1) find most frequent value in B; 2) discard all rows where B is not the most frequent value ?
– 4Oh4
Mar 8 at 22:46
add a comment |
Welcome to StackOverflow. Just to clarify - if I was to summarise what you are trying to achieve, you would: 1) find most frequent value in B; 2) discard all rows where B is not the most frequent value ?
– 4Oh4
Mar 8 at 22:46
Welcome to StackOverflow. Just to clarify - if I was to summarise what you are trying to achieve, you would: 1) find most frequent value in B; 2) discard all rows where B is not the most frequent value ?
– 4Oh4
Mar 8 at 22:46
Welcome to StackOverflow. Just to clarify - if I was to summarise what you are trying to achieve, you would: 1) find most frequent value in B; 2) discard all rows where B is not the most frequent value ?
– 4Oh4
Mar 8 at 22:46
add a comment |
1 Answer
1
active
oldest
votes
We can use mode to return the value that appears most often and then filter on that value:
df[df['B']==df['B'].mode()[0]]
Output:
A B
0 ! 1
1 @ 1
2 # 1
3 $ 1
And value_counts can be used for the Nth most frequent value (starting with N=0 being the most frequent) :
df[df['B']==df['B'].value_counts().index[N]]
e.g. for N=1:
df[df['B']==df['B'].value_counts().index[1]]
Output:
A B
4 % 2
6 & 2
9 ) 2
answered Mar 8 at 21:48
perlperl
1,908416
1
Thank you so much!! You are the best. I'm a new python user and am still learning.
– Amie Johnson
Mar 8 at 21:51
What if I wanted the 2nd or 3rd most frequent values?
– Amie Johnson
Mar 8 at 21:52
Updated my answer with how to filter on the Nth most frequent
– perl
Mar 8 at 21:59
Amazing, thank you again so much! Have a great weekend!
– Amie Johnson
Mar 8 at 22:07
1
@AmieJohnson (and perl, you should both get a notification): Welcome to the both of you to Stack Overflow! Please try to use comments as intended, see when not to comment: while "Thanks!" is polite, it's noise for any future readers. If you like this answer, please upvote it (and accept it if it answers your question) and pay it forward by helping others if you can!
– TemporalWolf
Mar 8 at 22:23
|
show 1 more comment
Your Answer
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1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
We can use mode to return the value that appears most often and then filter on that value:
df[df['B']==df['B'].mode()[0]]
Output:
A B
0 ! 1
1 @ 1
2 # 1
3 $ 1
And value_counts can be used for the Nth most frequent value (starting with N=0 being the most frequent) :
df[df['B']==df['B'].value_counts().index[N]]
e.g. for N=1:
df[df['B']==df['B'].value_counts().index[1]]
Output:
A B
4 % 2
6 & 2
9 ) 2
answered Mar 8 at 21:48
perlperl
1,908416
1
Thank you so much!! You are the best. I'm a new python user and am still learning.
– Amie Johnson
Mar 8 at 21:51
What if I wanted the 2nd or 3rd most frequent values?
– Amie Johnson
Mar 8 at 21:52
Updated my answer with how to filter on the Nth most frequent
– perl
Mar 8 at 21:59
Amazing, thank you again so much! Have a great weekend!
– Amie Johnson
Mar 8 at 22:07
1
@AmieJohnson (and perl, you should both get a notification): Welcome to the both of you to Stack Overflow! Please try to use comments as intended, see when not to comment: while "Thanks!" is polite, it's noise for any future readers. If you like this answer, please upvote it (and accept it if it answers your question) and pay it forward by helping others if you can!
– TemporalWolf
Mar 8 at 22:23
|
show 1 more comment
We can use mode to return the value that appears most often and then filter on that value:
df[df['B']==df['B'].mode()[0]]
Output:
A B
0 ! 1
1 @ 1
2 # 1
3 $ 1
And value_counts can be used for the Nth most frequent value (starting with N=0 being the most frequent) :
df[df['B']==df['B'].value_counts().index[N]]
e.g. for N=1:
df[df['B']==df['B'].value_counts().index[1]]
Output:
A B
4 % 2
6 & 2
9 ) 2
answered Mar 8 at 21:48
perlperl
1,908416
1
Thank you so much!! You are the best. I'm a new python user and am still learning.
– Amie Johnson
Mar 8 at 21:51
What if I wanted the 2nd or 3rd most frequent values?
– Amie Johnson
Mar 8 at 21:52
Updated my answer with how to filter on the Nth most frequent
– perl
Mar 8 at 21:59
Amazing, thank you again so much! Have a great weekend!
– Amie Johnson
Mar 8 at 22:07
1
@AmieJohnson (and perl, you should both get a notification): Welcome to the both of you to Stack Overflow! Please try to use comments as intended, see when not to comment: while "Thanks!" is polite, it's noise for any future readers. If you like this answer, please upvote it (and accept it if it answers your question) and pay it forward by helping others if you can!
– TemporalWolf
Mar 8 at 22:23
|
show 1 more comment
We can use mode to return the value that appears most often and then filter on that value:
df[df['B']==df['B'].mode()[0]]
Output:
A B
0 ! 1
1 @ 1
2 # 1
3 $ 1
And value_counts can be used for the Nth most frequent value (starting with N=0 being the most frequent) :
df[df['B']==df['B'].value_counts().index[N]]
e.g. for N=1:
df[df['B']==df['B'].value_counts().index[1]]
Output:
A B
4 % 2
6 & 2
9 ) 2
answered Mar 8 at 21:48
perlperl
1,908416
We can use mode to return the value that appears most often and then filter on that value:
df[df['B']==df['B'].mode()[0]]
Output:
A B
0 ! 1
1 @ 1
2 # 1
3 $ 1
And value_counts can be used for the Nth most frequent value (starting with N=0 being the most frequent) :
df[df['B']==df['B'].value_counts().index[N]]
e.g. for N=1:
df[df['B']==df['B'].value_counts().index[1]]
Output:
A B
4 % 2
6 & 2
9 ) 2
answered Mar 8 at 21:48
perlperl
1,908416
edited Mar 8 at 22:06
answered Mar 8 at 21:48
perlperl
1,908416
answered Mar 8 at 21:48
perlperl
1,908416
answered Mar 8 at 21:48
perlperl
1,908416
1,908416
1
Thank you so much!! You are the best. I'm a new python user and am still learning.
– Amie Johnson
Mar 8 at 21:51
What if I wanted the 2nd or 3rd most frequent values?
– Amie Johnson
Mar 8 at 21:52
Updated my answer with how to filter on the Nth most frequent
– perl
Mar 8 at 21:59
Amazing, thank you again so much! Have a great weekend!
– Amie Johnson
Mar 8 at 22:07
1
@AmieJohnson (and perl, you should both get a notification): Welcome to the both of you to Stack Overflow! Please try to use comments as intended, see when not to comment: while "Thanks!" is polite, it's noise for any future readers. If you like this answer, please upvote it (and accept it if it answers your question) and pay it forward by helping others if you can!
– TemporalWolf
Mar 8 at 22:23
|
show 1 more comment
1
Thank you so much!! You are the best. I'm a new python user and am still learning.
– Amie Johnson
Mar 8 at 21:51
What if I wanted the 2nd or 3rd most frequent values?
– Amie Johnson
Mar 8 at 21:52
Updated my answer with how to filter on the Nth most frequent
– perl
Mar 8 at 21:59
Amazing, thank you again so much! Have a great weekend!
– Amie Johnson
Mar 8 at 22:07
1
@AmieJohnson (and perl, you should both get a notification): Welcome to the both of you to Stack Overflow! Please try to use comments as intended, see when not to comment: while "Thanks!" is polite, it's noise for any future readers. If you like this answer, please upvote it (and accept it if it answers your question) and pay it forward by helping others if you can!
– TemporalWolf
Mar 8 at 22:23
1
1
Thank you so much!! You are the best. I'm a new python user and am still learning.
– Amie Johnson
Mar 8 at 21:51
Thank you so much!! You are the best. I'm a new python user and am still learning.
– Amie Johnson
Mar 8 at 21:51
What if I wanted the 2nd or 3rd most frequent values?
– Amie Johnson
Mar 8 at 21:52
What if I wanted the 2nd or 3rd most frequent values?
– Amie Johnson
Mar 8 at 21:52
Updated my answer with how to filter on the Nth most frequent
– perl
Mar 8 at 21:59
Updated my answer with how to filter on the Nth most frequent
– perl
Mar 8 at 21:59
Amazing, thank you again so much! Have a great weekend!
– Amie Johnson
Mar 8 at 22:07
Amazing, thank you again so much! Have a great weekend!
– Amie Johnson
Mar 8 at 22:07
1
1
@AmieJohnson (and perl, you should both get a notification): Welcome to the both of you to Stack Overflow! Please try to use comments as intended, see when not to comment: while "Thanks!" is polite, it's noise for any future readers. If you like this answer, please upvote it (and accept it if it answers your question) and pay it forward by helping others if you can!
– TemporalWolf
Mar 8 at 22:23
@AmieJohnson (and perl, you should both get a notification): Welcome to the both of you to Stack Overflow! Please try to use comments as intended, see when not to comment: while "Thanks!" is polite, it's noise for any future readers. If you like this answer, please upvote it (and accept it if it answers your question) and pay it forward by helping others if you can!
– TemporalWolf
Mar 8 at 22:23
|
show 1 more comment
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Welcome to StackOverflow. Just to clarify - if I was to summarise what you are trying to achieve, you would: 1) find most frequent value in B; 2) discard all rows where B is not the most frequent value ?
– 4Oh4
Mar 8 at 22:46