如何从数据框中创建一个以“c(df$lat,cd$lon)”和半径“df$radius”为中心的实心圆的栅格图层?
df <- data.frame(lat=c(40.4,42.4,42.4,42.4,42.3),
lon=c(-0.3,1,1.5,2.7,2.1),
radius=c(4.4,8.4,11.4,5.4,10.3))
df
# lat lon radius
# 40.4 -0.3 4.4
# 42.4 1.0 8.4
# 42.4 1.5 11.4
# 42.4 2.7 5.4
# 42.3 2.1 10.3