lurodrig - 6 months ago 23

R Question

I have a simple question, that I can't seem to find the answer to on google, stackoverflow or stackexchange. I am currently working with the example of

`rollapply`

`z <- zoo(c(NA, NA, NA, NA,2, 3, 4, 5, NA))`

rollapply(z, 3, sum, na.rm = TRUE, align = "right")

This outputs:

`3 4 5 6 7 8 9`

0 0 2 5 9 12 9

This looks good, however, there are two times where there are 3 NA's in a row. The sum feature exchanges NA's to 0's. Unfortunately, that won't work with the data I'm going to work with since 0 is a meaningful value. Is there a way to replace the 0's with NA's again?

I'm looking for an output as below:

`3 4 5 6 7 8 9`

NA NA 2 5 9 12 9

Thank you in advance!

Answer

You can do the following (even though not very nice)

```
require(zoo)
z <- zoo(c(NA, NA, NA, NA,2, 3, 4, 5, NA))
tmp <- rollapply(z, 3, sum, na.rm = TRUE, align = "right")
tmp[is.na(z)[-2:-1] & tmp == 0] <- NA
tmp
```

so you assign `NA`

wherever `z`

is na and there is a `NA`

produced by `rollapply`

which gives you:

```
> tmp
3 4 5 6 7 8 9
NA NA 2 5 9 12 9
```