-
-
Save tomhopper/edb10f680510d092cd56 to your computer and use it in GitHub Desktop.
careful when filtering with many groups in dplyr
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
library(dplyr) | |
# create a dummy dataframe with 100,000 groups and 1,000,000 rows | |
# and partition by group_id | |
df <- data.frame(group_id=sample(1:1e5, 1e6, replace=T), | |
val=sample(1:100, 1e6, replace=T)) %>% | |
group_by(group_id) | |
# filter rows with a value of 1 naively | |
system.time(df %>% filter(val == 1)) | |
# user system elapsed | |
# 1.447 0.017 1.476 | |
# ungroup before filtering for a huge speedup | |
system.time(df %>% ungroup() %>% filter(val == 1)) | |
# user system elapsed | |
# 0.007 0.003 0.010 |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment