Using apply with Spatial*DataFrame

Question

Suppose I have the following SpatialPointsDataFrame

library(sp)
exdf <- data.frame(cbind(1:10, 41:50, 101:110))
names(exdf) <- c("id", "x", "y")
coordinates(exdf) <- c("x", "y")

I can run the following apply

apply(exdf@data, 1, function(x) { 
                      cat(coordinates(exdf[exdf$id == x["id"],]), "\n") 
                                })

However it seems ridiculous to select from the same data frame within the function. I'm already iterating through it.

Note that, in my actual use, I need to send both the data frame row and the coordinates to another function, so applying only on the exdf@coords is not an option.

Question 1: Is there a way to do this without exdf[exdf$id == x["id"],] part?

Question 2: If not, is there a package that I can use instead of sp for such tasks. I need sp for its over function primarily, and checked also spatstat and decided sp is simpler to use. However using a "data frame" that's not actually a data.frame annoys me.

Thank you.

Answer 1

You can easily transform your SpatialPointsDataFrame into a regular data.frame and then proceed from there:

> df <- as.data.frame(exdf)
> df
   id  x   y
1   1 41 101  
2   2 42 102
3   3 43 103
4   4 44 104
5   5 45 105
6   6 46 106
7   7 47 107
8   8 48 108
9   9 49 109
10 10 50 110
> paste(df$x, df$y, sep=' ')
 [1] "41 101" "42 102" "43 103" "44 104" "45 105" "46 106" "47 107" "48 108" "49 109" "50 110"

Edit: From the comment, the OP would like to achieve the result in simpler ways but without converting the Spatial*DataFrame into a data.frame. The same result as in his example can be achieved with the following code, but it needs to be changed if additional columns would also be printed/concatenated/processed:

cat(paste(exdf@coords[,1], exdf@coords[,2]), sep='\n')