Remove characters from list which contains numeric and characters without NA coercion message

I've got a list which contains numbers and text items. I want to remove the text items and keep the numeric items. I don't mind using a few lines of code, So I can do the below with with x, then remove the NAs using another line. BUT I want to avoid the NAs coercion warning message.

x <- c(1,"_2",3 , 6 , "1_" , "a")
as.numeric(x)
[1]  1 NA  3  6 NA NA
Warning message:
NAs introduced by coercion 

Any help is greatly appreciated. Thanks in advance.

You could use grep from base R to get values that only contain digits ie ^\\d+$ or use \\D to get those that contain non-digits and invert the regex to match only digits:

as.numeric(grep("\\D", x, value = TRUE, invert = TRUE))
[1] 1 3 6
as.numeric(grep("^\\d+$", x, value = TRUE))
[1] 1 3 6

We can use suppressWarnings to muffle the warnings

suppressWarnings(as.numeric(x))
[1]  1 NA  3  6 NA NA

Or with str_subset

library(tidyr)
as.numeric(str_subset(x, "^\\d+$"))
[1] 1 3 6
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