Neelay Trivedi - 11 months ago 55

R Question

I am trying to understand why na.rm would be used inside of the mean() function in R. Specifically, I am trying to figure out the difference between na.rm =TRUE and na.rm=FALSE.

Answer

`na.rm = TRUE`

takes out any `NA`

values that could potentially be in the vector you are taking the `mean`

of. If there is even 1 `NA`

value in your vector and `na.rm = FALSE`

the result will be `NA`

. Here's a basic example:

```
a <- c(1,2,3,4,NA,6)
> mean(a, na.rm = FALSE)
[1] NA
```

If you choose `na.rm = TRUE`

it will take the mean of all the values in the vector that aren't `NA`

:

```
> mean(a, na.rm = TRUE)
[1] 3.2
```

Note that if you don't include the `na.rm`

argument in your function the default is `na.rm = FALSE`

.

```
> mean(a)
[1] NA
```

Source (Stackoverflow)