Hi there,
I am interested in calculating precipitation medians globally. However, I only
want to isolate land areas to compute the median. I already first created a
raster stack, called "RCP1pctCO2median", which contains the median values.
There are 138 layers, with each layer representing one year. This raster stack
has the following attributes:
class : RasterStack
dimensions : 64, 128, 8192, 138 (nrow, ncol, ncell, nlayers)
resolution : 2.8125, 2.789327 (x, y)
extent : -181.4062, 178.5938, -89.25846, 89.25846 (xmin, xmax, ymin, ymax)
coord. ref. : +proj=longlat +datum=WGS84 +ellps=WGS84 +towgs84=0,0,0
names : layer.1, layer.2, layer.3, layer.4, layer.5,
layer.6, layer.7, layer.8, layer.9, layer.10, layer.11,
layer.12, layer.13, layer.14, layer.15, ...
min values : 0.42964514, 0.43375653, 0.51749371, 0.50838983, 0.45366730,
0.53099146, 0.49757186, 0.45697752, 0.41382199, 0.46082401, 0.45516687,
0.51857087, 0.41005131, 0.45956529, 0.47497867, ...
max values : 96.30350, 104.08584, 88.92751, 97.49373, 89.57201,
90.58570, 86.67651, 88.33519, 96.94720, 101.58247, 96.07792,
93.21948, 99.59785, 94.26218, 90.62138, ...
Previously, I was isolating a specific region by specifying a range of
longitudes and latitudes to obtain the medians for that region, like this:
expansion1<-expand.grid(103:120, 3:15)lonlataaa<-extract(RCP1pctCO2Median,
expansion1)Columnaaa<-colMeans(lonlataaa)
However, with this approach, too much water can mix with land areas, and if I
narrow the latitude/longitude range on land, I might miss too much land to
compute the median meaningfully.
Therefore, with this data, would it be possible to use an IF/ELSE statement to
tell R that if the "center point" of each grid cell happens to fall on land,
then it would be considered as land (i.e. that would be TRUE - if not, then
FALSE)? Even if a grid cell happens to have water mixed with land, but the
center point of the grid is on land, that would be considered land. But can R
even tell what is land or water in this case?
Thank you, and I would greatly appreciate any assistance!
[[alternative HTML version deleted]]
_______________________________________________
R-sig-Geo mailing list
R-sig-Geo@r-project.org
https://stat.ethz.ch/mailman/listinfo/r-sig-geo
