ggplot2 and cumsum() – Stackify

Here’s a test data which uses plyr‘s transform to calculate the cumulative sum first and then apply that data to plot using ggplot2:

DF <- data.frame(grp = factor(rep(1:5, each=10)), x=rep(1:10, 5))
DF <- transform(DF, y=runif(nrow(DF)))

# use plyr to calculate cumsum per group of x
DF.t <- ddply(DF, .(grp), transform, cy = cumsum(y))

# plot
ggplot(DF.t, aes(x=x, y=cy, colour=grp, group=grp)) + geom_line()

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