R 如何获取ggmap中top-N最大密度点坐标
我对热图有问题。我可以通过ggmap和眼球看到热图上最密集的地方,但我如何才能得到这些点的确切长度和纬度呢。以下是测试代码:R 如何获取ggmap中top-N最大密度点坐标,r,ggplot2,ggmap,R,Ggplot2,Ggmap,我对热图有问题。我可以通过ggmap和眼球看到热图上最密集的地方,但我如何才能得到这些点的确切长度和纬度呢。以下是测试代码: set.seed(1) mymap <- get_map(location = "Detroit", zoom = 8) mydata <- data.table(long = runif(min = -84, max = -82.5, n = 100), lat = runif(min = 42, max = 42.
set.seed(1)
mymap <- get_map(location = "Detroit", zoom = 8)
mydata <- data.table(long = runif(min = -84, max = -82.5, n = 100),
lat = runif(min = 42, max = 42.7, n = 100))
g <- ggmap(mymap) +
stat_density2d(data = mydata,
aes(x = long, y = lat, fill = ..level..,alpha = ..level..),
size = 0.5, bins = 10, geom = "polygon") +
scale_alpha_continuous(range(0.1,0.5))
g
set.seed(1)
mymapgeom\u density\u 2d的帮助说明:
Description:
Perform a 2D kernel density estimation using ‘kde2d’
kde2d
功能位于MASS
包中
阅读相关文档,您将了解如何从ggplot
正在绘制的内核密度中获取值矩阵
然后问题归结为寻找矩阵的局部极大值:
仅供参考,您应该使您的代码在新的R会话中可复制,因此无论什么library()
语句都需要在顶部(如下面的答案所示)。
> library(MASS); library(raster)
> w = matrix(1,3,3)
> x = kde2d(mydata$long, mydata$lat, n=100)
> r = raster(x)
> f <- function(X) max(X, na.rm=TRUE)
> localmax <- focal(r, w, fun = f, pad=TRUE, padValue=NA)
> r2 <- r==localmax
> maxXY <- xyFromCell(r2, Which(r2==1, cells=TRUE))
> image(x,asp=1)
> points(maxXY)
> maxXY
x y
[1,] -82.86796 42.43167
[2,] -83.47583 42.34163
[3,] -82.83831 42.18924