R reorders data when changing bar color. How do I prevent this?

Question

So, I have a dataset which I want to draw as bars. However, R re-orders my dataset as soon as I add colors!

library("ggplot2")

data <- read.csv(file = "data.csv",
                 stringsAsFactors = TRUE)

# This is what I want position-wise
plot <- ggplot(data, aes(y=median,x=backend)) +
  geom_bar(stat = "identity", aes(fill=generic), position = position_dodge2(padding = .2), alpha = 0.75) +
  labs(title="Median", y="", x="Backends",fill="Generic")
print(plot)

# This is what I want color-wise
anydsl.plot <- ggplot(data, aes(y=median,x=backend)) +
  geom_bar(stat = "identity", aes(fill=ifelse(generic, "Yes", "No")), position = position_dodge2(padding = .2), alpha = 0.75) +
  labs(title="Median", y="", x="Backends", fill="Generic")
print(plot)

The dataset is as follows:

backend,median,minimum,maximum,generic,threads
cpu,8.70,8.40,14.06,1,1
cpu,8.10,7.65,13.23,0,1
cpu,5.77,5.54,10.04,1,2
cpu,5.42,4.24,9.34,0,2
cpu,4.44,4.12,7.07,1,3
cpu,4.26,3.79,6.82,0,3
cpu,3.70,3.52,6.42,1,4
cpu,3.77,3.48,6.04,0,4
cpu,3.49,3.20,5.40,1,5
cpu,3.53,3.08,5.45,0,5
cpu,3.42,3.08,5.23,1,6
cpu,3.51,3.20,4.79,0,6
cpu,3.46,3.17,4.84,1,7
cpu,3.48,2.98,4.75,0,7
cpu,3.46,3.14,4.76,1,8
cpu,3.47,3.12,4.60,0,8
avx,4.49,4.47,8.85,1,1
avx,4.33,4.31,8.53,0,1
avx,3.58,3.27,6.10,1,2
avx,3.49,3.25,5.99,0,2
avx,3.38,2.97,5.36,1,3
avx,3.40,3.01,5.31,0,3
avx,3.43,2.98,4.62,1,4
avx,3.38,2.84,4.72,0,4
avx,3.40,2.93,4.60,1,5
avx,3.42,2.95,4.53,0,5
avx,3.43,2.97,4.49,1,6
avx,3.42,2.80,4.47,0,6
avx,3.46,3.06,4.49,1,7
avx,3.45,2.91,4.50,0,7
avx,3.46,2.98,5.18,1,8
avx,3.47,2.98,4.42,0,8
cuda,3.04,2.98,3.10,1,1
cuda,0.33,0.32,0.34,0,1
nvvm,3.40,3.33,3.46,1,1
nvvm,2.72,2.68,2.77,0,1
opencl,3.04,3.00,3.09,1,1
opencl,0.33,0.32,0.34,0,1

The output without my custom colors is:

The output with my custom colors is:

How do I get the first plot but with the colors of the second?

Answer 1

The issue is that by mapping ifelse(generic, "Yes", "No") on fill you implictily change the grouping variable. To get the same grouping as in your first plot map backend on the group aes

library(ggplot2)
library(dplyr)

data <- read.table(text = "backend,median,minimum,maximum,generic,threads
cpu,8.70,8.40,14.06,1,1
cpu,8.10,7.65,13.23,0,1
cpu,5.77,5.54,10.04,1,2
cpu,5.42,4.24,9.34,0,2
cpu,4.44,4.12,7.07,1,3
cpu,4.26,3.79,6.82,0,3
cpu,3.70,3.52,6.42,1,4
cpu,3.77,3.48,6.04,0,4
cpu,3.49,3.20,5.40,1,5
cpu,3.53,3.08,5.45,0,5
cpu,3.42,3.08,5.23,1,6
cpu,3.51,3.20,4.79,0,6
cpu,3.46,3.17,4.84,1,7
cpu,3.48,2.98,4.75,0,7
cpu,3.46,3.14,4.76,1,8
cpu,3.47,3.12,4.60,0,8
avx,4.49,4.47,8.85,1,1
avx,4.33,4.31,8.53,0,1
avx,3.58,3.27,6.10,1,2
avx,3.49,3.25,5.99,0,2
avx,3.38,2.97,5.36,1,3
avx,3.40,3.01,5.31,0,3
avx,3.43,2.98,4.62,1,4
avx,3.38,2.84,4.72,0,4
avx,3.40,2.93,4.60,1,5
avx,3.42,2.95,4.53,0,5
avx,3.43,2.97,4.49,1,6
avx,3.42,2.80,4.47,0,6
avx,3.46,3.06,4.49,1,7
avx,3.45,2.91,4.50,0,7
avx,3.46,2.98,5.18,1,8
avx,3.47,2.98,4.42,0,8
cuda,3.04,2.98,3.10,1,1
cuda,0.33,0.32,0.34,0,1
nvvm,3.40,3.33,3.46,1,1
nvvm,2.72,2.68,2.77,0,1
opencl,3.04,3.00,3.09,1,1
opencl,0.33,0.32,0.34,0,1", sep = ",", header = TRUE)

# This is what I want color-wise
anydsl.plot <- ggplot(data, aes(y=median,x=backend, group = backend)) +
  geom_bar(stat = "identity", aes(fill = ifelse(generic, "Yes", "No")), position = position_dodge2(padding = .2), alpha = 0.75) +
  labs(title="Median", y="", x="Backends", fill="Generic")
print(anydsl.plot)