I have three SpatialPointsDataFrame objects that are actually just one point each. My intention is to make a raster for each of them with an extent that includes the point, in such a way that all cells but the point are "NA", so then I can use the distance() function in the package raster to generate a raster layer where the z value is the distance to the only cell in which z is not "NA".
My code works without problem with the first of the three objects, but the following error appears for the other two:
error in seq.default(zrng[1], zrng[2], length.out = cuts + 2) :
'from' cannot be NA, NaN or infinite
In addition: Warning messages:
1: In asMethod(object) :
complete map seems to be NA's -- no selection was made
2: In min(x) : no non-missing arguments to min; returning Inf
3: In max(x) : no non-missing arguments to max; returning -Inf
I have double and triple checked that my points are contained in the extent of the raster, and I really can't pinpoint the problem
Here's my code:
library(raster)
TIM <- data.frame()
TIM[1,1] <- -13.8309
TIM[1,2] <- 28.9942
VEN <- data.frame()
VEN[1,1] <- -15.7886
VEN[1,2] <- 27.8444
MCL <- data.frame()
MCL[1,1] <- -13.5325
MCL[1,2] <- 29.2914
coordinates(TIM) <- ~V1+V2
coordinates(VEN) <- ~V1+V2
coordinates(MCL) <- ~V1+V2
bb2 <- matrix(c(-20, -9.5, 20.5, 31.5), nrow = 2, ncol = 2, byrow = T)
bb2 <- extent(bb2)
r <- raster(nrows = 1217, ncols = 1047)
r <- setExtent(r, bb2, keepres=F)
rMCL <- rasterize(MCL, r)
spplot(rMCL)
#so far so good, but from now on it doesn't work
rVEN <- rasterize(VEN, r)
spplot(rVEN)
rTIM <- rasterize(TIM, r)
spplot(rTIM)
Edit: I have tried turning it to a SpatialGridDataFrame and I get to plot it but my point is not in the extent of the raster, i.e. the plot is empty. Code:
rr <- as(rTIM, "SpatialGridDataFrame")
spplot(rr)
#this produces an empty plot
I have also tried plotting it in a raster without a predetermined number of columns and rows, and it works:
r <- raster()
r <- setExtent(r, bb2, keepres=F)
rTIM <- rasterize(TIM, r)
spplot(rTIM)
# this produces a raster containing my point
The problem is, I really would need to set the resolution of the plot so each cell of the raster represents approx 1 squared km, which is what I get with the number of rows and columns I had previously used. Any ideas?
I can get it to work by adding all three sets of coordinates to the same dataframe and then using the count function when creating the raster:
library(raster)
# Add all 3 sets of coordinates to the same dataframe
df <- data.frame()
df[1,1] <- -13.8309
df[1,2] <- 28.9942
df[2,1] <- -15.7886
df[2,2] <- 27.8444
df[3,1] <- -13.5325
df[3,2] <- 29.2914
# Create new column in dataframe (we will use this for the count function)
df$x <- c(1,1,1)
# Convert to spatial points dataframe
df.sp <- df
coordinates(df.sp) <- ~ V1+V2
# Make raster
bb2 <- matrix(c(-20, -9.5, 20.5, 31.5), nrow = 2, ncol = 2, byrow = T)
bb2 <- extent(bb2)
r <- raster(nrows = 1217, ncols = 1047)
r <- setExtent(r, bb2, keepres=F)
# Rasterise using the count function
raster <- rasterize(df.sp, r, field= "x", fun="count")
# The table shows there are 3 cells with a value of 1 so it seems to have worked
table(values(raster))
1
3
spplot(raster)
raster
class : RasterLayer
dimensions : 1217, 1047, 1274199 (nrow, ncol, ncell)
resolution : 0.01002865, 0.00903862 (x, y)
extent : -20, -9.5, 20.5, 31.5 (xmin, xmax, ymin, ymax)
coord. ref. : +proj=longlat +datum=WGS84 +ellps=WGS84 +towgs84=0,0,0
data source : in memory
names : layer
values : 1, 1 (min, max)
The plot doesn't make a whole lot of sense to me but I think that's because you have a lot of cells in your raster so you can't really see anything. The values in the raster are definitely 3 cells with a value of 1 and all the rest are NA so I think this what you want.