如何在R的色标中强制将零映射为白色 [英] how to force map zero to white color in R plotly color scale

问题描述

下面是我的代码，但我想将白色映射为0，而不是data_bydate $ avg_score的最大值和最小值的中间值

My code is the following but I would like to have white color mapped to 0 instead of the middle values of the max and min of data_bydate$avg_score

g <- plot_ly(data_bydate, x = ~Date, y = ~avg_score, color =data_bydate$avg_score, colors = c("#FF0000","#FFFFFF", "#008000"), mode ='markers', marker = list(size=3)) %>%
layout(legend = list(orientation = 'h'), 
       xaxis = list(title = "",
                    zeroline = FALSE,
                    tickformat="%X",
                    showline = TRUE), 
       yaxis = list(title = "",
                    zeroline = FALSE,
                    showline = TRUE ))

现在它没有给出零以上的图值是绿色，而零以下是红色...

Right now it doesn't give a graph where the above zero values are green and below zero values are red...

推荐答案

您可以创建自己的 colorscale ，从红色（最小）到白色（零）到绿色（最大）。 colorscale 是由两个单独的色阶组成的数组列表，一个色阶为零以下的部分，从红色到白色，另一个为以上色阶，从白色到绿色。 。

You could create your own colorscale which goes from red (min) to white (zero) to greenish (max). The colorscale is a list of arrays which is composed of two separate colorscales, one for the part below zero, from red to white, and the other one above, from white to green.

library(plotly)
library(scales)

set.seed(42)
colorlength <- 100

data_bydate <- data.frame(Date = c(1:23),
                          avg_score = c(runif(10, -5, -1), 
                                        rep(0,3), 
                                        runif(10, 1, 10)
                                        )
                          )

null_value <- (0 - min(data_bydate$avg_score)) / (max(data_bydate$avg_score) - min(data_bydate$avg_score))        
border <- as.integer(null_value * colorlength)
colorscale <- as.list(1:colorlength)

#colorscale below zero
s <- scales::seq_gradient_pal("#FF0000", "#FFFFFF", "Lab")(seq(0,1,length.out=border))
for (i in 1:border) {
    colorscale[[i]] <- c((i - 1) / colorlength, s[i])
}

#colorscale above zero
s <- scales::seq_gradient_pal("#FFFFFF", "#008000", "Lab")(seq(0,1,length.out=colorlength - border))
for (i in 1:(colorlength - border)) {
  colorscale[[i + border]] <- c((i + border) / colorlength, s[i])
}

plot_ly(data_bydate, 
        x = ~Date, 
        y = ~avg_score, 
        type = 'scatter',
        mode ='markers', 
        marker = list(size = 10,
                      color = ~avg_score,
                      colorscale = colorscale,
                      colorbar = list(len=1))) %>%
  layout(plot_bgcolor = 'black')

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