Thank you Frans. This is exactly the sort of nuance that I want to learn
about.
--Chris
Frans Marcelissen wrote:
Hello Christopher and others
:
What cannot be stressed enough is: do not combine both packages, it
gives errors and incorrect results! I will show that below
--------------------------------------------------------
a<-data.frame(groep=1:4,v=1:40)
library(dplyr)
a %>% group_by(groep) %>% summarise(m=mean(v),n=n())
# groep m n
# <int> <dbl> <int>
# 1 1 19 10
# 2 2 20 10
# 3 3 21 10
# 4 4 22 10
# correct
library(plyr)
a %>% group_by(groep) %>% summarise(m=mean(v),n=n())
Error in n() : This function should not be called directly
# ???
a %>% group_by(groep) %>% summarise(m=mean(v))
# m
# 1 20.5
#incorrect!
--------------------------------------------------
So both n() and group_by from dplyr don't work after library(plyr)!
My advice is: do not use plyr. Unfortunately plyr has some functions
that are very important, and that are not in dplyr. For
instance: rbind.fill() (for combining the rows of two dataframes with
unequal columns). If you need this: do'nt library plyr, use plyr::rbind.fil
Until now I have the impression that it is also possible to library
dplyr after plyr, but it is better to remove plyr!
This is a serious problem that has been reported before, but not solved
(in dplyr 0.5.0 and plyr 1.8.4)
Frams
2016-09-15 16:09 GMT+02:00 Christopher W Ryan <cr...@binghamton.edu
<mailto:cr...@binghamton.edu>>:
I've set myself the task of learning about these packages, and about
tidy data concepts.
What is the relationship between plyr and dplyr? Does the latter
replace the former (meaning I can concentrate on learning the latter)?
Or is there ever a need to use functions from both (meaning I should
learn both)?
Thanks.
--Chris Ryan
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