dyRibbon中调色板颜色的顺序是什么？

Question

考虑使用 R 中dygraphs包的dyRibbon函数的 reprex 的这些问题。

Q1。 为什么 3 色带显示需要 4 种颜色？ 为什么第一个总是被忽略？

Q2。 色带调色板的顺序是如何分配给每个数值的？ 正如您将在下面的代表中看到的那样，它肯定不是按照数字顺序

library(data.table)
library(dygraphs)
library(RColorBrewer)
library(dplyr)

set.seed(12)
# create data
dt1 <- data.table(t = seq(Sys.time(),by  = "1 sec", length.out = 10),
                  y = rnorm(10,20,5))
# add a column with 3 possible values to be used for dyRibbon
dt1[,flag1:=factor(dplyr::case_when(y>22 ~ "high",y>18 ~ "med", T ~ "low"))]
dt1[,rflagn:=as.numeric(flag1)]

# generate the dygraph with a 3 color ribbon
dyg1 <- 
  dt1 %>% 
  select(t,y) %>% 
  dygraph(main = "Reprex to show color sequence") %>% 
  dyOptions(drawPoints = T,pointSize = 5,drawGapEdgePoints = T,
            strokeWidth = 4,strokeBorderWidth = 1) %>% 
  dyRibbon(dt1$rflagn/4,palette = brewer.pal(4,"Set1"))

# checkout the reprex graph paying attention to the sequence of colors
dyg1

# check the sequence of colors in the palette
display.brewer.pal(4,"Set1")

# check the actual values in first 10 rows
dt1
#>                       t        y flag1 rflagn
#>  1: 2022-05-18 21:47:10 12.59716   low      2
#>  2: 2022-05-18 21:47:11 27.88585  high      1
#>  3: 2022-05-18 21:47:12 15.21628   low      2
#>  4: 2022-05-18 21:47:13 15.39997   low      2
#>  5: 2022-05-18 21:47:14 10.01179   low      2
#>  6: 2022-05-18 21:47:15 18.63852   med      3
#>  7: 2022-05-18 21:47:16 18.42326   med      3
#>  8: 2022-05-18 21:47:17 16.85872   low      2
#>  9: 2022-05-18 21:47:18 19.46768   med      3
#> 10: 2022-05-18 21:47:19 22.14007  high      1

Answer 1

我在 rstudio 社区得到了答案。 解决方案是必须明确定义序列。

data_arg <- dt1 %>% 
    mutate(flagn = case_when(
        flag1 == "low" ~ 0,
        flag1 == "med" ~ 0.5,
        flag1 == "high" ~ 1)) %>% 
    pull(flagn)

一旦定义了它，我们只需将它传递给dyRibbon 。

...
dyRibbon(data = data_arg, palette = brewer.pal(3,"Set1"))

所以我依赖于可能是任意的因子的默认序列。 最好明确定义 data 参数。

感谢https://community.rstudio.com/t/how-does-the-sequence-of-palette-color-in-dyribbon-get-decided/137559/2?u=sanjmeh