Assume df:

```
A   B   C   D   E   F
1   10  NA  10  NA  10
10  NA  10  1   10  10
10  1   1   NA  NA  NA
10  10  NA  10  10  10
10  NA  10  10  1   10

```

What I wish to do is to loop through columns to check values for each rows with following conditions:

* A < 5 or NA
* C < 3 or NA
* E < 7 or NA
* F < 2 or NA

...and subsequently, with rows in the looped column matching respective condition, the entire row will be pushed to NA

Desired outcome:

```
A   B   C   D   E   F
NA  NA  NA  NA  NA  NA
10  NA  10  1   10  10
NA  NA  NA  NA  NA  NA
NA  NA  NA  NA  NA  NA
NA  NA  NA  NA  NA  NA

```

I tried doing this to one of the columns:

```
df[df$A<5, ] <- NA

```

However this caused the error of

```
Error in `[<-.data.frame`(`*tmp*`, df$A < 5, , value = NA) : 
  missing values are not allowed in subscripted assignments of data frames

```

Please advise