Question

I’m running a monte-carlo simulation and the output is in the form:

> d = data.frame(iter=seq(1, 2), k1 = c(0.2, 0.6), k2=c(0.3, 0.4))
> d
iter  k1   k2
1     0.2  0.3
2     0.6  0.4

The plots I want to generate are:

plot(d$iter, d$k1)
plot(density(d$k1))

I know how to do equivalent plots using ggplot2, convert to data frame

new_d = data.frame(iter=rep(d$iter, 2), 
                   k = c(d$k1, d$k2), 
                   label = rep(c('k1', 'k2'), each=2))

then plotting is easy. However the number of iterations can be very large and the number of k’s can also be large. This means messing about with a very large data frame.

Is there anyway I can avoid creating this new data frame?

Thanks

Answer 1

Short answer is “no,” you can’t avoid creating a data frame. ggplot requires the data to be in a data frame. If you use qplot, you can give it separate vectors for x and y, but internally, it’s still creating a data frame out of the parameters you pass in.

I agree with juba’s suggestion — learn to use the reshape function, or better yet the reshape package with melt/cast functions. Once you get fast with putting your data in long format, creating amazing ggplot graphs becomes one step closer!