使用RColorBrewer使颜色在0附近居中

Question

所以我想要可视化一个矩阵，它有这样的颜色

library(RColorBrewer)
vec = rbinom(10000,1,0.1)
n = sum(vec)
vec = ifelse(vec == 1, rnorm(n), 0)
mat = matrix(vec,100,100)
image(t(mat)[,nrow(mat):1],
      col=brewer.pal(8,"RdBu"),
      xaxt= "n", yaxt= "n", frame.plot=T,
      useRaster = TRUE
)

这就给了我一个情节

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但我希望颜色“以0为中心”。我的意思是，我希望值0为白色，正值/负值为红/蓝(或蓝/红，没关系)。如果这是可能的，有什么想法吗？

Answer 1

gplots包中的函数bluered可以做到这一点。您可以将调色板设置为：

library(gplots) # not to be confused with `ggplot2`, which is a very different package
color_palette <- bluered(9) # change the number to adjust how many shades of blue/red you have.  Even numbers will assign white to two bins in the middle.

要强制它们居中，也可以在gplots中使用heatmap.2函数-只是不要让它进行任何聚类：

heatmap.2(mat,
  Rowv = FALSE,
  Colv = FALSE, 
  dendrogram = 'none',
  trace = 'none',
  col = bluered, # this can take a function
  symbreaks = TRUE, # this is the key  value for symmetric breaks
)

要继续使用image函数，您需要手动设置分隔符。下面的代码将为您实现这一点：

pos_breaks <- quantile(abs(mat), probs = seq(0, 1, length.out = 5))
centered_breaks <- c(rev(-pos_breaks[-1]), pos_breaks)

Answer 2

这是一个不需要任何额外包的解决方案。在您的代码中，您没有将来自vec变量的值分配给八个颜色箱中的任何一个。您需要将vec数组分成8个存储箱，然后为每个存储箱分配颜色，然后绘制：

library(RColorBrewer)
vec = rbinom(10000,1,0.1)
n = sum(vec)
vec = ifelse(vec == 1, rnorm(n), 0)
mat = matrix(vec,100,100)

#cut the original data into 9 groups
cutcol<-cut(vec, 9)
#Create color palette with white as the center color
colorpal<-brewer.pal(8,"RdBu")
colorpal<-c(colorpal[1:4], "#FFFFFF", colorpal[5:8])

#assign the data to the 9 color groups
color<-colorpal[cutcol]
#create the color matrix to match the original data
colormat<-matrix(color,100,100)

#plot with the assigned colors
image(t(mat)[,nrow(mat):1],
      col=colormat,
      xaxt= "n", yaxt= "n", frame.plot=T,
      useRaster = TRUE
)

#check color assignment
#hist(vec)
#hist(as.numeric(cutcol), breaks=8)

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Answer 3

除了heatmap2，您还可以使用pheatmap

library(pheatmap)
pheatmap(mat,
         color = brewer.pal(7,"RdBu"),
         border_color = NA,
         cluster_rows = FALSE,
         cluster_cols = FALSE)

如果愿意，您还可以使用legend = FALSE隐藏图例，这将产生与图像调用类似的结果，但白色为0。