Rounding selected columns of data.table in R
I have following data and code to round selected columns of this data.table:
> dput(mydf)
structure(list(vnum1 = c(0.590165705411504, -1.39939534199836,
0.720226053660755, -0.253198380120377, -0.783366825121657), vnum2 = c(0.706508400384337,
0.526770398486406, 0.863136084517464, 0.838245498016477, 0.556775856064633
), vch1 = structure(c(2L, 4L, 1L, 3L, 3L), .Label = c("A", "B",
"C", "E"), class = "factor")), .Names = c("vnum1", "vnum2", "vch1"
), row.names = c(NA, -5L), class = c("data.table", "data.frame"
))
> mydf[,round(.SD,1),]
Error in Math.data.frame(list(vnum1 = c(0.590165705411504, -1.39939534199836, :
non-numeric variable in data frame: vch1
> cbind(mydf[,3,with=F], mydf[,1:2,with=F][,round(.SD,1),])
vch1 vnum1 vnum2
1: B 0.6 0.7
2: E -1.4 0.5
3: A 0.7 0.9
4: C -0.3 0.8
5: C -0.8 0.6
Is there a better method (shorter code)? Thanks for your help.
Using dplyr
If you want to round multiple columns at once:
mydf %>% mutate_at(vars(vnum1, vnum2), funs(round(., 1)))
Or, if you want to change all columns except "vch1":
mydf %>% mutate_at(vars(-vch1), funs(round(., 1)))
Or, if you want to change all columns starting with "vnum":
mydf %>% mutate_at(vars(starts_with("vnum")), funs(round(., 1)))
Or, if you want to change only numeric columns:
mydf %>% mutate_if(is.numeric, ~round(., 1))
You get:
vnum1 vnum2 vch1
1 0.6 0.7 B
2 -1.4 0.5 E
3 0.7 0.9 A
4 -0.3 0.8 C
5 -0.8 0.6 C
If you don't mind overwriting your original mydf
:
cols <- names(mydf)[1:2]
mydf[,(cols) := round(.SD,1), .SDcols=cols]
mydf
# vnum1 vnum2 vch1
#1: 0.6 0.7 B
#2: -1.4 0.5 E
#3: 0.7 0.9 A
#4: -0.3 0.8 C
#5: -0.8 0.6 C