How to order colour fill on geom_col?

Question

Hi, I'm trying to change the order of values on X axis of geom_col and by using factor() and scale_x_discrete() functions and it worked but and the same time the colour order changed.

colors <- c("#f2f0f7", "#dadaeb", "#bcbddc", "#9e9ac8", "#756bb1", "#54278f")    
positions <- c("P1", "P8", "P3", "P4", "P5", "P6")
positions <- factor(positions, levels = c("P1", "P8", "P3", "P4", "P5", "P6")) # order on legend

ggplot() + 
  scale_x_discrete(limits = positions) + 
  geom_col(data=a, aes(x = X, y = M, fill = positions), width = 0.75, position = position_dodge(0.1), colour = "black", size = 0.9) +
  labs(title = paste(Rname, Tname, sep = " ")) + xlab(Rname) + ylab(Tname) +
  coord_cartesian(ylim = c(0, NA)) +
  geom_errorbar(data=a, aes(x = X, y = M, ymin = M, ymax = max), width=0.5, size=1) +
  scale_fill_manual(values = colors, breaks = positions) + 
  scale_y_continuous(expand=c(0,0), limits = c(0,max(df2$Y, na.rm = TRUE)*1.05)) + 
  
  theme_set(theme_classic(base_size = 30, base_family = "Helvetica", base_line_size = 1)) +
  theme(
    aspect.ratio = 5/4,
    axis.line.y.left = element_line(),
    
    axis.text = element_text(hjust = 1, color = "black"),
    axis.text.x = element_text(angle=45),
    axis.text.y = element_text(angle=0),
    
    axis.title.x.bottom = element_text(size = 22, angle=0, margin = margin(t=20)),
    axis.title.y = element_text(size = 22, angle=0, margin = margin(r = 20), vjust = 0.5),
    plot.title = element_text(size = 30, margin = margin(b = 30), hjust = 0.5 ),
    
    axis.ticks.y = element_line(),
    axis.ticks.length.y = unit(10,"pt"), 
  )

I managed to changed it back to normal by changing the order of colours in scale_fill_manual:

scale_fill_manual(values = c("#f2f0f7", "#bcbddc", "#9e9ac8", "#756bb1", "#54278f", "#dadaeb"), breaks = positions) + 

but it messed up the legend colour order... Could you please guide me in the right direction where both the x axis and colour order are preserved on both plot and the legend?

Answer 1

The main error is to have two variables for the same x axis, X and positions . The graph only needs positions .

I will focus on getting the colors in their right places, the other layers can then be added.

library(ggplot2)

ggplot(a, aes(positions, M, fill = positions)) + 
  geom_col(width = 0.75, position = position_dodge(0.1), colour = "black", size = 0.9) +
  scale_x_discrete(limits = positions) + 
  coord_cartesian(ylim = c(0, NA)) +
  scale_fill_manual(values = colors, breaks = positions) +
  theme_bw()

Data

set.seed(2020)    # needed to make the y axis values reproducible

colors <- c("#f2f0f7", "#dadaeb", "#bcbddc", "#9e9ac8", "#756bb1", "#54278f")
positions <- c("P1", "P8", "P3", "P4", "P5", "P6")
positions <- factor(positions, levels = c("P1", "P8", "P3", "P4", "P5", "P6")) # order on legend
M <- sample(10, length(positions), TRUE)
a <- data.frame(M, positions, colors)