Applying color gradients to columns

Numeric trends in larger tables can quickly become difficult to see. Adding color to reveal these trends can be one way to make reading complex tables a little easier.

Excuse the contrived nature of the data below, but I really want to make a rainbow gradient!

using StyledTables, DataFrames, Colors

df = DataFrame(id = 1:8, score = rand(8))

8×2 DataFrame

Row	id	score
	Int64	Float64
1	1	0.0699432
2	2	0.962072
3	3	0.905078
4	4	0.0294121
5	5	0.354725
6	6	0.999883
7	7	0.634254
8	8	0.348413

So far so boring.

The gradient we'll be applying is the following:

colors = range(HSV(0,1,1), stop = HSV(-360,1,1), length = nrow(df))

Step 1: Styling function

The function below is more general than what would be required for the specific example here. In our case, it would be possible to simply use the id variable to index into colors.

function apply_gradient(x, xmax; colors)
    color = colors[round(Int, (x / xmax) * length(colors))]
    return (; color)
end

apply_gradient (generic function with 1 method)

Step 2: Apply styling

tbl = StyledTable(df)
style!(x -> apply_gradient(x, maximum(df.id); colors), tbl, :id)
render(tbl)

id	score
1	0.0699
2	0.962
3	0.905
4	0.0294
5	0.355
6	1
7	0.634
8	0.348

Step 3: Column labels

relabel!(tbl, :id => "Student ID", :score => "Score")
render(tbl)

Student ID	Score
1	0.0699
2	0.962
3	0.905
4	0.0294
5	0.355
6	1
7	0.634
8	0.348