Question: I have a website which has a contact form. The form is sent to a outlook.com email. And in this outlook.com account I have a redirection rule configured to redirect to salesforce. The funny thing is, sometimes the redirection works perfect but sometimes it does not work (I monitored in salesforce and I have no reception of email). But in those cases If the automatic redirections fails, I do a manual redirection, and the email is received. 
Does anyone experienced a similar situation between outlook.com redirections with salesforce? Is there something related to outlook.com or salesforce?

Answer: 
You could do this...

```
df[,sapply(df,function(x) 4 %in% x)]

  column_three column_four
1            3           3
2            4           4

```
Following on from @AndrewGustar's answer, here's an equivalent solution using `dplyr`:

```r
library(dplyr)
select_if(df, function(x) 4 %in% x)

#>   column_three column_four
#> 1            3           3
#> 2            4           4

```