How to better create stacked bar graphs with multiple variables from ggplot2?

Question

I often have to make stacked barplots to compare variables, and because I do all my stats in R, I prefer to do all my graphics in R with ggplot2. I would like to learn how t

Answer 1

Your second problem can be solved with melt and cast from the reshape package

After you've factored the elements in your data.frame called you can use something like:

install.packages("reshape")
library(reshape)

x <- melt(your.df, c()) ## Assume you have some kind of data.frame of all factors
x <- na.omit(x) ## Be careful, sometimes removing NA can mess with your frequency calculations

x <- cast(x, variable + value ~., length)
colnames(x) <- c("variable","value","freq")
## Presto!
ggplot(x, aes(variable, freq, fill = value)) + geom_bar(position = "fill") + coord_flip() + scale_y_continuous("", formatter="percent")

As an aside, I like to use grep to pull in columns from a messy import. For example:

x <- your.df[,grep("int.",df)] ## pulls all columns starting with "int_"

And factoring is easier when you don't have to type c(' ', ...) a million times.

for(x in 1:ncol(x)) { 
df[,x] <- factor(df[,x], labels = strsplit('
Very Interested
Somewhat Interested
Not Very Interested
Not At All interested
NA
NA
NA
NA
NA
NA
', '\n')[[1]][-1]
}