How to change stacking order in stacked bar chart in R?

Question

I have a dataset like this:

> ra
   quality     GY         TH         SZ         DZ         FP
1        B 25.5932389 23.0215577 21.2171520 23.7548859 19.9         


        

Answer 1

I think quality is stacked in the original order: B, F, M and so on. I suppose it is the order of the legend what you'd like to change:

ra.melt$quality <- factor(ra.melt$quality, levels = ra$quality)
p <- ggplot(ra.melt, aes(x = variable, y = value))
p + geom_bar(aes(fill = quality), stat = "identity") + 
    labs(x = "group", y = "percentage (%)")

Or in reverse order:

ra.melt$quality <- factor(ra.melt$quality, levels = rev(ra$quality))
p <- ggplot(ra.melt, aes(x = variable, y = value))
p + geom_bar(aes(fill = quality), stat = "identity") +  
    labs(x = "group", y = "percentage (%)")

Notes

The legend takes the levels of the factor, which are sorted alphabetically by default:

levels(ra.melt$quality)
# Output
 [1] "A"     "B"     "C"     "D"     "E"     "F"     "G"     
     "H"     "I"     "J"     "K"     "L"     "M"     "other"

With ra.melt$quality <- factor(ra.melt$quality, levels = ra$quality) we set the order of the levels of the factor as they originally occur in the vector:

levels(ra.melt$quality)
#Output:
[1] "B"     "F"     "M"     "A"     "G"     "E"     "J"   
    "D"     "C"     "I"     "K"     "L"     "H"     "other"