[R] subsetting - questions

[Muhuri, Pradip (SAMHSA/CBHSQ)]

Hello,

I have two very basic questions (console attached):

1) What am I getting an error message for  # 5 and # 7 ?
2) How to fix the code?

I would appreciate receiving your help.

Thanks,

Pradip Muhuri



###### Reproducible Example  #####

N <- 100
set.seed(13)
df<-data.frame(matrix(sample(c(1:10),N, replace=TRUE),ncol=5))

keep_var <- c("X1", "X2")
drop_var <- c("X3", "X4", "X5")


df[df$X1>=8,] [,1:2]                   #1
df[df$X1>=8,] [,-c(3,4,5)]             #2
df[df$X1>=8,] [,c(-3,-4,-5)]           #3
df[df$X1>=8,] [,c("X1", "X2")]         #4
df[df$X1>=8,] [,-c("X3", "X4", "X5")]  #5  DOES NOT WORK
df[df$X1>=8,] [,keep_var]              #6
df[df$X1>=8,] [, !drop_var]            #7   DOES NOT WORK