grouped barplot: order x-axis & keep constant bar width, in case of missing levels

Question

Here is my script (example inspired from here and using the reorder option from here):

library(ggplot2)
Animals <- read.table(
  header=TRUE, tex         


        

Answer 1

Along the same lines as the answer from user Alex, a less manual way of adding the categories might be

d <- with(Animals, expand.grid(unique(Category), unique(Reason)))
names(d) <- names(Animals)[1:2]
Animals <- merge(d, Animals, all.x=TRUE)
Animals$Species[is.na(Animals$Species)] <- 0

Answer 2

To achieve something like that I would adjust the data frame when working with ggplot. Add the missing categories with a value of zero.

Animals <- rbind(Animals, 
                 data.frame(Category = c("Improved", "Decline"), 
                            Reason = c("Hello", "Bla"), 
                            Species = c(0,0)
                            )
)

Answer 3

First let's fill your data.frame with missing combinations like this.

library(dplyr)
Animals2 <- expand.grid(Category=unique(Animals$Category), Reason=unique(Animals$Reason)) %>% data.frame %>% left_join(Animals)

Then you can create an ordering variable for the x-scale:

myorder <- Animals2 %>% filter(Category=="Decline") %>% arrange(desc(Species)) %>% .$Reason %>% as.character

An then plot:

ggplot(Animals2, aes(x=Reason, y=Species, fill = Category)) + 
  geom_bar(stat="identity", position = "dodge") + scale_x_discrete(limits=myorder)

Answer 4

Define new data frame with all combinations of "Category" and "Reason", merge with data of "Species" from data frame "Animals". Adapt ggplot by correct scale_x_discrete:

Animals3 <-  expand.grid(Category=unique(Animals$Category),Reason=unique(Animals$Reason))
Animals3 <- merge(Animals3,Animals,by=c("Category","Reason"),all.x=TRUE)
Animals3[is.na(Animals3)] <- 0
Animals3 <- Animals3[order(Animals3$Category,-Animals3$Species),]
ggplot(Animals3, aes(x=Animals3$Reason, y=Species, fill = Category)) + geom_bar(stat="identity", position = "dodge") + scale_x_discrete(limits=as.character(Animals3[Animals3$Category=="Decline","Reason"]))