Sequential palettes for data stored in a list-CodePudding

Hopefully someone here will be able to give me a hint. I have a customized function, which plots the curves from the data stored in different list's elements. I have more than one curve in each element of the list. To each of those curves is related a numeric value, for instance going from 0.1 to 2. So basically I also have a list where each element contains the numeric values related to the curves in that element. I need to plot those curves with a different color, darker for the ones corresponding to the small values and lighter for the ones corresponding to higher values, regardless to which list element they belong. What I need in my function is a list from which I can choose the color for each of the curves. So, for instance, I have a list a: a=list(c(1,2,3),c(8,4,1)).

How can I build a color Palette and assign it the same list structure, such that to 1 corresponds a dark color, to 2 a lighter color, to 8 the lightest color and so on? The important difference here is that in the "a" there are only 5 different values, while in the real case there are 88 different continuous values raging from 1 to 13. I can normalize them so they are between 0 and 1 but still those are 88 different colors/shades of the colors. I was going through the similar topics here but could find anything which would help me to make any progress on this issue. Thank you in advance.

CodePudding user response：

We can use scales::col_numeric here. It takes a vector of colors and the numeric domain over which you wish to apply them, and returns interpolated colors for a given numeric input value. We can write a function that applies this to your list, by getting the minimum and maximum numbers in your list as the domain, then doing an lapply with scales::col_numeric

make_colors <- function(my_list, low = 'red4', high = 'pink') {

  lowest  <- min(unlist(my_list))
  highest <- max(unlist(my_list))
  
  lapply(my_list, function(x) {
    scales::col_numeric(c(low, high), c(lowest, highest))(x)
  })
}

Let's try this on your own example.

a <- list(c(1,2,3), c(8,4,1))

make_colors(a)
#> [[1]]
#> [1] "#8B0000" "#9E2A1D" "#B14538"
#> 
#> [[2]]
#> [1] "#FFC0CB" "#C25D53" "#8B0000"

Note that the structure of the output is the same as the structure of the input, with each element in each vector of the original list having a color assigned to it based on its value.

We can see how these colors look by plotting them. Since we are using the numbers in the list a both for the y position and the color, we should that the lightness of each point is determined by how high it is.

plot(unlist(a), cex = 3, pch = 16, col = unlist(make_colors(a)))

Of course, you are free to change the colors of the lowest and highest points to whichever you feel most appropriate.

CodePudding user response：

Without a minimal working example, it is hard to fully understand what you are expecting. But I would take a guess and say you should experiment with scale_color_manual().