Arihant - 4 months ago 37

R Question

I have a binary raster(r) at 1 meter resolution and I want to convert it into a percentage value at 4m resolution.This new raster would have each pixel value representing the percent, calculated on basis of total frequency of 1 out of four pixels.I looked at the

`raster`

`aggregate`

`newras <-aggregate(r, fact=4, fun= percent)`

Answer

What you do does not work because there is no function called `percentage`

. But you can make one. In this case, the mean value is the fraction, so you multiply that with 100 to get the percentage.

Example data

```
library(raster)
r <- raster()
set.seed(0)
values(r) <- sample(0:1, ncell(r), replace=TRUE)
```

Aggregate

```
a <- aggregate(r, 4, fun=function(x,...) 100 * mean(x))
# or
a <- 100 * aggregate(r, 4, mean)
```

Consider `NA`

values

```
r[sample(ncell(r), 0.9 * ncell(r))] <- NA
# Make a function and use it
percentage <- function(x, ...) { x <- na.omit(x); 100 * mean(x) }
a <- aggregate(r, 4, fun=percentage)
# or do
a <- 100 * aggregate(r, 4, fun=mean, na.rm=TRUE)
```