将值映射到颜色映射颜色

Question

我有一个介于0和1之间的数字列表，并希望使用scale_color_gradient2提供的算法将它们映射到HEX颜色值。默认颜色值low = muted("red"), mid = "white", high = muted("blue")工作得很好。我需要HEX值本身，而不是在图上着色对象。

使用matplotlib在Python作为被要求here，但我需要做的这R.

Answer 1

的scale_color_gradient2功能使用着色功能从scales库类似的问题。你可以得到一个转换功能与

library(scales) 
trans <- div_gradient_pal(muted("red"), mid="white", high=muted("blue"), space="Lab") 

然后再应用此功能，您的号码

cols <- trans(seq(0,1, length.out=20)) 
plot(1:20, 1:20, col=cols) 

Answer 2

您也可以使用colorRamp功能从基础R的值映射到RGB颜色，然后使用rgb函数转换为十六进制格式。

一个例子：

# I use hex numbers between 0.3 and 0.7 (instead of O and 1) to show that the ggplot scale used the 
# minimum and maximum values by defaults (as done in the python examples you provided) 
set.seed(123) 
d <- data.frame(
    hex = sort(runif(20, 0.3, 0.7)), 
    x = 1:20, 
    y = 1 
) 

# Graph with ggplot and scale_fill_gradient2 
ggplot(d, aes (x, y, fill = hex)) + geom_bar(stat = "identity") + 
    scale_fill_gradient2 (low = "red", mid = "white", high = "blue", midpoint = 0.5) 


# Normalize the vector to use the minimum and maximum values as extreme values 
hexnorm <- (d$hex - min(d$hex))/(max(d$hex) - min(d$hex)) 

# Map the hex values to rgb colors 
mycols <- colorRamp(c("red", "white", "blue"), space = "Lab")(hexnorm) 
# Transform the rgb colors in hexadecimal format 
mycols <- rgb(mycols[,1], mycols[,2], mycols[,3], maxColorValue = 255) 
mycols 

# Check that you obtain the same result as the scale_fill_gradient2 ggplot function 
ggplot(d, aes (x, y)) + geom_bar(stat = "identity", fill = mycols)