Select rows of a data.frame that contain only numbers in a certain column

Question

How to select only the rows that contain a number in column b.

a <- c(1,5,3,1,-8,6,-1)
b <- c(4,-2,1,0,\"c\",2,\"DX\")

df <- data.frame(a,         


        

Answer 1

This should be faster (it doesn't use regex)

df[!is.na(as.numeric(df$b)), ]

Answer 2

You could use grep:

df[grep("[[:digit:]]", df$b), ]
#  a  b
#1 1  4
#2 5 -2
#3 3  1
#4 1  0
#6 6  2