Colours don't show up in bar plot using ggplot2 - ggplot2

Question

When I try to assign colours using colour = "" or fill = """, the graph changes its colour always to the same colour (some kind of weird orange tone). The specific code I used is this:
Plot <- ggplot(data, aes(ymin = 0)) + geom_rect(aes(xmin = left, xmax = right, ymax = a, colour = "#FDFEFE")).
Has anyone had this problem before? It doesn`t seem to matter whether I use the colour names or the HTML codes, the result stays the same.
Thank you!

Answer 1

I just wanted to add some explanation because this also tripped me up when I started using ggplot.
Some toy data:
data <- tibble(a = 1:10, left = 1:10 * 20, right = 1:10 * 20 + 10)
As explained by #stefan, you need to set the hard-coded color outside of the aestetics:
ggplot(data, aes(ymin = 0)) +
geom_rect(aes(xmin = left, xmax = right, ymax = a), fill = "#FDFEFE")
The aestetics are meant to link the plot to your data table. When you write this:
ggplot(data, aes(ymin = 0)) +
geom_rect(aes(xmin = left, xmax = right, ymax = a, fill = "#FDFEFE"))
It is like having the following:
data <- tibble(a = 1:10, left = 1:10 * 20, right = 1:10 * 20 + 10, col = "#FDFEFE")
ggplot(data, aes(ymin = 0)) +
geom_rect(aes(xmin = left, xmax = right, ymax = a, fill = col))
Except that ggplot understands "#FDFEFE" as a categorical value, not as a color. Having "#FDFEFE" or "banana" is the same to ggplot:
ggplot(data, aes(ymin = 0)) +
geom_rect(aes(xmin = left, xmax = right, ymax = a, fill = "banana"))
or
data <- tibble(a = 1:10, left = 1:10 * 20, right = 1:10 * 20 + 10, col = "banana")
ggplot(data, aes(ymin = 0)) +
geom_rect(aes(xmin = left, xmax = right, ymax = a, fill = col))
assign default colours to the categorical data.
As an extra, if you want to assign specific colors to different entries in the table, it is best to use a scale_*_manual layer:
data <- tibble(a = 1:10, left = 1:10 * 20, right = 1:10 * 20 + 10,
col = sample(c("banana", "orange", "coconut"), 10, replace = T))
ggplot(data, aes(ymin = 0)) +
geom_rect(aes(xmin = left, xmax = right, ymax = a, fill = col)) +
scale_fill_manual(values = c("banana" = "yellow2", "orange" = "orange2", "coconut" = "burlywood4"))
If you wanted to hard-code the colors in the table, you would have to use this column outside to the aestetics:
data <- tibble(a = 1:10, left = 1:10 * 20, right = 1:10 * 20 + 10,
col = sample(c("yellow2", "orange2", "burlywood4"), 10, replace = T))
ggplot(data, aes(ymin = 0)) +
geom_rect(aes(xmin = left, xmax = right, ymax = a), fill = data$col)
But it is best to use meaningful categorical values and assign the colors in the scale layer. This is what the grammar of graphics is all about!