Reorder heatmap by specific group in R

Question

Using the airline-safety dataset available here, I'm trying to create a heat map in R. I want to order the heat map so that the airlines with the highest number of fatal accidents are listed at the top.

I'm able to order the heat map by "value" -

but this orders the heatmap by value, regardless of what the group is i.e. incidents, fatal accidents or fatalities.

# load packages -----------
library(tidyverse)
library(ggplot2)
library(reshape2)
library(dplyr)
library(plyr)
library(scales)
library(forcats)

# read in the data
airlines <- read.csv("/Volumes/GoogleDrive/My Drive/Uni/DVN/AT2/Blog 2/airline_incidents.csv", header = TRUE) 

# select relevant columns 
airlines_00_14 <- airlines[,c(1,6,7,8)]

# create a long dataset
airlines_00_14.m <- melt(airlines_00_14) 

# rescale values for heat map 
airlines_00_14.m <- ddply(airlines_00_14.m, .(variable), transform, rescale = rescale(value))

# create heat map 
(q <- airlines_00_14.m %>%
    ggplot( aes(x = variable, y = reorder(airline, value))) + 
    geom_tile(aes(fill = rescale), colour = "white") + 
    scale_fill_gradient(low = "white", high = "steelblue")) 

Answer 1

One way to do this is to create the order before you melt, like this:

# order by fatalities and generate air_order value
airlines_00_14 = airlines_00_14[order(airlines_00_14$fatal_accidents_00_14),]
airlines_00_14$air_order = seq_len(nrow(airlines_00_14))

Then, when you use reshape2::melt, set `id.vars = c("airline","air_order")

# create a long dataset
airlines_00_14.m <- reshape2::melt(airlines_00_14,id.vars = c("airline", "air_order"))

Then, in your plot, use y=reorder(airline, air_order) instead of the current y=reorder(airline, value)

Output: