Given a sample data frame:
C1<-c(3,2,4,4,5)
C2<-c(3,7,3,4,5)
C3<-c(5,4,3,6,3)
DF<-data.frame(ID=c("A","B","C","D","E"),C1=C1,C2=C2,C3=C3)
DF
ID C1 C2 C3
1 A 3 3 5
2 B 2 7 4
3 C 4 3 3
4 D 4 4 6
5 E 5 5 3
What is the best way to create a second data frame that would contain the ID
column and the mean of each row? Something like this:
ID Mean
A 3.66
B 4.33
C 3.33
D 4.66
E 4.33
Something similar to:
RM<-rowMeans(DF[,2:4])
I'd like to keep the means aligned with their ID
's.
(Another solution using pivot_longer
& pivot_wider
from latest Tidyr
update)
You should try using pivot_longer to get your data from wide to long form Read latest tidyR update on pivot_longer & pivot_wider (https://tidyr.tidyverse.org/articles/pivot.html)
library(tidyverse)
C1<-c(3,2,4,4,5)
C2<-c(3,7,3,4,5)
C3<-c(5,4,3,6,3)
DF<-data.frame(ID=c("A","B","C","D","E"),C1=C1,C2=C2,C3=C3)
Output here
ID mean
<fct> <dbl>
1 A 3.67
2 B 4.33
3 C 3.33
4 D 4.67
5 E 4.33
Using dplyr:
library(dplyr)
# exclude ID column then get mean
DF %>%
transmute(ID,
Mean = rowMeans(select(., -ID)))
Or
# select the columns to include in mean
DF %>%
transmute(ID,
Mean = rowMeans(select(., C1:C3)))
# ID Mean
# 1 A 3.666667
# 2 B 4.333333
# 3 C 3.333333
# 4 D 4.666667
# 5 E 4.333333
Starting with your data frame DF
, you could use the data.table
package:
library(data.table)
## EDIT: As suggested by @MichaelChirico, setDT converts a
## data.frame to a data.table by reference and is preferred
## if you don't mind losing the data.frame
setDT(DF)
# EDIT: To get the column name 'Mean':
DF[, .(Mean = rowMeans(.SD)), by = ID]
# ID Mean
# [1,] A 3.666667
# [2,] B 4.333333
# [3,] C 3.333333
# [4,] D 4.666667
# [5,] E 4.333333
You can create a new row with $
in your data frame corresponding to the Means
DF$Mean <- rowMeans(DF[,2:4])
rowMeans
is nice, but if you are still trying to wrap your head around the apply
family of functions, this is a good opprotunity to begin understanding it.
DF['Mean'] <- apply(DF[,2:4], 1, mean)
Notice I'm doing a slightly different assignment than the first example. This approach makes it easier to incorporate it into for loops.
Source: Stackoverflow.com