geom_point colors not correct using ggplot2

Question

I'm stumped as to why my points are incorrectly coloured. I have set my own colour palette and used this to define the colours of the geom_point() but the colours that are actually being plotted are incorrect.

colfunc <- colorRampPalette(c("black", "#FFAFAF"))
plot(rep(1,41), col=colfunc(41), pch=19, cex=3)

cols <- colfunc(41)

df$cols <- cols[df$num]

baseMap <- ggplot(data = world) +
  geom_sf(color = "black", fill = "grey") +
  geom_point(data = df, 
             mapping = aes(x = lon, y = lat, col = cols[num])) +
  xlab("Longitude") + ylab("Latitude")

baseMap

The colour palette I have created looks like this:

Colour palette

But this is resulting in the following colours:

Resulting colours

Why aren't these colours matching??

Thanks

I have tried numerous different ways of setting the aes() but can't work out why the colours don't match

Answer 1

You need scale_colour_manual() or similar. We do not have your df. This is an example based on another df:

library(ggplot2)
colfunc <- colorRampPalette(c("black", "#FFAFAF"))
# plot(rep(1,41), col=colfunc(41), pch=19, cex=3)
cols <- colfunc(41)
world <-ggplot2::map_data(map = "world")

set.seed(1)
df <- data.frame(lon = runif(41, min(world$long), max(world$long)),
                 lat = runif(41, min(world$lat), max(world$lat)), 
                 id = 1:41, cols = cols)

ggplot(world, aes(x = long, y = lat)) + 
  geom_polygon(aes(group = group), colour = "grey") +
  geom_point(data = df, 
             mapping = aes(x = lon, y = lat, 
                           colour = factor(id))) +
  scale_colour_manual(values = df$cols) +
  xlab("Longitude") + ylab("Latitude")

^{Created on 2023-11-18 with reprex v2.0.2}