[R-sig-Geo] Question on Aggregation

[Loïc Dutrieux]

On 14/01/2017 14:02, Miluji Sb wrote:
> I have the following GDP data by longitude and latitude at 0.5 degree by
> 0.5 degree.
> 
> temp <- dput(head(ptsDF,10))
> structure(list(longitude = c(-68.25, -67.75, -67.25, -68.25,
> -67.75, -67.25, -71.25, -70.75, -69.25, -68.75), latitude = c(-54.75,
> -54.75, -54.75, -54.25, -54.25, -54.25, -53.75, -53.75, -53.75,
> -53.75), GDP = c(1.683046, 0.3212307, 0.0486207, 0.1223268, 0.0171909,
> 0.0062104, 0.22379, 0.1406729, 0.0030038, 0.0057422)), .Names =
> c("longitude",
> "latitude", "GDP"), row.names = c(4L, 17L, 30L, 43L, 56L, 69L,
> 82L, 95L, 108L, 121L), class = "data.frame")
> 
> I would like to aggregate the data 1 degree by 1 degree. This is what I
> have done:
> 
> temp$long1 <- floor(temp$longitude)
> temp$lat1 <- floor(temp$latitude)
> temp1 <- aggregate(GDP ~ long1 + lat1, temp, mean)
> 
> I was wondering though if I should be doing using sum instead of mean for
> aggregation, as in:

I think so. I'm not an expert in GDP but clearly it sounds like a
variable that "adds up" (it represents a quantity) and should therefore
be spatially aggregated with a sum.

Cheers,
Loïc
> 
> temp <- aggregate(GDP ~ long1 + lat1, temp, sum)
> 
> Any advice would be highly appreciated. Thank you!
> 
> Sincerely,
> 
> Milu
> 
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