我想创建一个以0为中心的颜色渐变。
以下代码:
library(raster)
librayr(RColorBrewer)
xmin = -124.413
xmax = -66.883
ymin = 25.9425
ymax = 48.9885
nrows = 215
ncols = 254
empty_raster = raster(xmn=xmin, ymn=ymin, nrows = nrows, ncols = ncols)
zscores_coords = cbind(seq(from=-124.413, to=-66.883, length.out=1212),
seq(from=25.9425, to=48.9885, length.out=1212))
zscores_raster = rasterize(zscores_coords, empty_raster, field = 1)
x_coord_raster = rasterize(zscores_coords, zscores_raster,
field=zscores_coords[,1])
y_coord_raster = rasterize(zscores_coords, zscores_raster,
field=zscores_coords[,2])
BUD_zscores_coordinates =
data.frame(x = zscores_coords[,1], y = zscores_coords[,2],
BUD_zscores = seq(from=-20.51558, to=14.34510, length.out=1212))
coordinates(BUD_zscores_coordinates) = ~x+y
zscores_pres = rasterize(BUD_zscores_coordinates, zscores_raster, field=1)
zscores_points = rasterToPoints(zscores_pres)
zscores_points = zscores_points[,c(1:2)]
zscores_nodes = rasterize(BUD_zscores_coordinates, empty_raster,
field = BUD_zscores_coordinates$BUD_zscores,
fun = mean)
#Plot!
colorramp = brewer.pal(11,"RdBu")
applycolors = colorRampPalette(colorramp)
plot(zscores_nodes, xlim = c(xmin, xmax), ylim = c(ymin, ymax),
col = applycolors(100))
生成以下图形:
其中“0”位于颜色渐变的浅蓝色部分。有关如何使其与白色部分对齐的任何建议?我一直在努力使用休息无济于事。
答案 0 :(得分:2)
使用这个答案:https://stackoverflow.com/a/10986203/4632634,我能够得到我所需要的问题。
library(raster)
library(RColorBrewer)
xmin = -124.413
xmax = -66.883
ymin = 25.9425
ymax = 48.9885
nrows = 215
ncols = 254
empty_raster = raster(xmn=xmin, ymn=ymin, nrows = nrows, ncols = ncols)
zscores_coords = cbind(seq(from=-124.413, to=-66.883, length.out=1212),
seq(from=25.9425, to=48.9885, length.out=1212))
zscores_raster = rasterize(zscores_coords, empty_raster, field = 1)
x_coord_raster = rasterize(zscores_coords, zscores_raster,
field=zscores_coords[,1])
y_coord_raster = rasterize(zscores_coords, zscores_raster,
field=zscores_coords[,2])
BUD_zscores_coordinates =
data.frame(x = zscores_coords[,1], y = zscores_coords[,2],
BUD_zscores = seq(from=-20.51558, to=14.34510, length.out=1212))
coordinates(BUD_zscores_coordinates) = ~x+y
zscores_pres = rasterize(BUD_zscores_coordinates, zscores_raster, field=1)
zscores_points = rasterToPoints(zscores_pres)
zscores_points = zscores_points[,c(1:2)]
zscores_nodes = rasterize(BUD_zscores_coordinates, empty_raster,
field = BUD_zscores_coordinates$BUD_zscores,
fun = mean)
zscores_stack = stack(zscores_nodes, zscores_raster, x_coord_raster,
y_coord_raster)
zscores_table = extract(zscores_stack, zscores_points)
#Plot! (bluer = flyway zscores > eBird szcores; red = eBird zscores >
#flyway zscores)
nHalf = nrow(zscores_table)/2
Min = min(zscores_table[,1])
Max = max(zscores_table[,1])
Thresh = 0
## Make vector of colors for values below threshold
rc1 = colorRampPalette(colors = c("red", "white"), space="Lab")(nHalf)
## Make vector of colors for values above threshold
rc2 = colorRampPalette(colors = c("white", "blue"), space="Lab")(nHalf)
rampcols = c(rc1, rc2)
## In your example, this line sets the color for values between 49 and 51.
rampcols[c(nHalf, nHalf+1)] = rgb(t(col2rgb("white")), maxColorValue=256)
rb1 = seq(Min, Thresh, length.out=nHalf+1)
rb2 = seq(Thresh, Max, length.out=nHalf+1)[-1]
rampbreaks = c(rb1, rb2)
r.range = c(Min, Max)
plot(zscores_nodes, xlim = c(xmin, xmax), ylim = c(ymin, ymax),
col = rampcols, breaks=rampbreaks, legend.width = 1, legend.shrink = 0.75,
axis.args=list(at=c(-20, 0, 14), labels=c(-20, 0, 14),
cex.axis=0.6),
legend.args=list(text='Z-Score', side=4, font=2, line=2.5, cex=0.8))
产生这个:
其中0很好地以白色区域为中心。