R中心调色板在0

使用以下答案：https : //stackoverflow.com/a/10986203/4632634，我能够获得解决问题所需的东西。

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))

产生此：

0恰好位于白色区域的中心。