[R-sig-Geo] Question on Aggregation

[Miluji Sb]

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:

temp <- aggregate(GDP ~ long1 + lat1, temp, sum)

Any advice would be highly appreciated. Thank you!

Sincerely,

Milu

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