Dear all,
I tried to use the code below to generate 3 X 3 grid of latitude-longitude
data. I use image to view the grid. However, latitude and longitude are on
the wrong axes. Thus, I want to swap the axes. I tried to swap x and y in:
image(x, ..) that did not help. I also wish to add color code to the plot.
Thanks for kind help.
portion of the data:
-3.3851 -65.3236
-3.2696 -65.2364
-3.2679 -65.2349
-17.6404 164.7025
-4.8285 148.8214
2.6477 -67.6568
-0.2350 -73.4833
-16.8655 40.9587
8.1179 -61.6474
-0.2755 93.3401
-17.1733 119.9011
1.1245 -69.7640
-20.0035 -149.3088
-3.4200 177.8753
3.0133 -67.5590
15.4684 -21.9331
-17.6166 120.2656
-17.3888 165.9368
-17.6953 164.7335
-1.8623 -74.0017
-3.3562 -71.1195
-11.5775 130.1496
code:
xy<-matrix(c(x, y), ncol=2)
# 3 deg grid for counts
grid3 <- matrix(0, nrow=120, ncol=60)
# accumulate counts of points in cells
for (i in 1:nrow(xy)) {
if (xy[i, 1] == 180)
ix = nrow(grid3)
else
ix <- floor((xy[i,1] + 180) / 3) + 1
if (xy[i, 2] == 90)
iy = ncol(grid3)
else
iy <- floor((xy[i,2] + 90) / 3) + 1
# catch any subscript errors
tryCatch(
grid3[ix, iy] <- grid3[ix, iy] + 1,
error = function(e) cat("Ignoring point out of bounds:", xy[i,], "\n") )
}
rb<-rev(rainbow(255,s=1,v=1,start=0,end=7/12,gamma=1,alpha=1))
image( x = seq(-88.5, 88.5, 3), y = seq(-178.5, 178.5, 3), z = t(grid3),
col=rb, ylab = "Longitude", xlab="Latitude" )
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