Plotting function goes wrong when adding new parameter - r

Question

I'm a beginneR using R Studio with R version 3.1.2 (2014-10-31) -- "Pumpkin Helmet" in Windows 7.
Data I'm using...
> dput(head(data,20))
structure(list(case = c(1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1), age = c(37, 42, 44, 40, 26, 29, 42, 26,
18, 56, 29, 66, 71, 26, 30, 48, 39, 65, 65, 48), bmi = c(25.95,
29.07, 27.63, 27.4, 25.34, 31.38, 25.08, 28.01, 24.69, 25.06,
27.68, 23.51, 29.86, 21.72, 25.95, 22.86, 23.53, 21.3, 33.2,
29.39), ord.bmi = c(3, 3, 3, 3, 3, 4, 3, 3, 2, 3, 3, 2, 3, 2,
3, 2, 2, 2, 4, 3), alcohol = c(2, 2, 1, 1, 2, 1, 1, 1, 1, 1,
2, 1, 1, 1, 1, 1, 2, 2, 1, 1), tobacco = c(1, 1, 1, 2, 2, 1,
2, 2, 1, 1, 2, 2, 1, 2, 1, 1, 2, 2, 1, 1), dent.amalgam = c(1,
2, 2, 1, 1, 1, 2, 2, 1, 1, 1, 2, 1, 2, 1, 2, 1, 1, 2, 1), exp.years = c(7,
9, 9, 5, 2, 10, 15, 5, 1, 40, 10, 50, 50, 1, 12, 22, 22, 30,
40, 30), mn = c(0, 0, 0, 1.5, 1.5, 1, 0, 0, 0.5, 0.5, 1, 1, 0,
0, 0, 0.5, 0, 0.5, 2, 1), bn = c(2.5, 5, 2.5, 2, 1.5, 4, 2, 1.5,
4.5, 4.5, 2.5, 2, 6, 2, 5, 4, 1, 1.5, 7, 1.5), ln = c(0.5, 1.5,
0, 2, 1.5, 1.5, 1, 0.5, 2, 2, 1, 1, 4.5, 0, 2, 1, 3, 2, 3, 3),
pn = c(0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0.5,
0.5, 0.5, 0, 0), cc = c(0, 1, 0, 2, 2, 4, 1, 1.5, 4.5, 2,
0, 3.5, 2, 1.5, 2, 1.5, 0.5, 1, 2, 1.5), kr = c(0, 0, 0,
0, 0, 0, 0.5, 0, 0.5, 1, 0, 0.5, 1.5, 0.5, 0.5, 0.5, 0, 0.5,
0, 0), kl = c(0.5, 2, 0, 1.5, 1.5, 0, 2, 0, 2, 2, 0, 1.5,
1.5, 1, 4, 3, 2, 3.5, 4.5, 2)), .Names = c("case", "age",
"bmi", "ord.bmi", "alcohol", "tobacco", "dent.amalgam", "exp.years",
"mn", "bn", "ln", "pn", "cc", "kr", "kl"), row.names = c(NA,
20L), class = "data.frame")
I'm plotting two different densities (which I get using density.a <- lapply(data[which(data$case == 0),], density) and density.b <- lapply(data[which(data$case == 1),], density)), and everything seems to work fine:
plot.densities <- function(sample.a, sample.b){ # declaring the function arguments
for(i in seq(length(sample.a))){ # for every element in the first argument (expected equal lengths)
plot(range(sample.a[[i]]$x, sample.b[[i]]$x), # generate a plot
range(sample.a[[i]]$y, sample.b[[i]]$y),
xlab = names(sample.a[i]), ylab = "Density", main = paste(names(sample.a[i]), "density plot"))
lines(sample.a[[i]], col = "red") # red lines
lines(sample.b[[i]], col = "green") #green lines
}
}
When I call the function, I get plots like this:
Then, if I want to fill the line between the two curves, I add the polygon function and looks like this:
filled.plot <- function(sample.a, sample.b){ # declaring the function arguments
for(i in seq(length(sample.a))){ # for every element in the first argument (expected equal lengths)
plot(range(sample.a[[i]]$x, sample.b[[i]]$x), # generate a plot
range(sample.a[[i]]$y, sample.b[[i]]$y),
xlab = names(sample.a[i]), ylab = "Density",
main = paste(names(sample.a[i])))
lines(sample.a[[i]], col = "red") # red lines
lines(sample.b[[i]], col = "green") #green lines
polygon(x = c(range(sample.a[[i]]$x, sample.b[[i]]$x),
rev(range(sample.a[[i]]$x, sample.b[[i]]$x))),
y = c(range(sample.a[[i]]$y, sample.b[[i]]$y),
rev(range(sample.a[[i]]$x, sample.b[[i]]$x))),
col = "skyblue")
}
}
But when I call the filled.plot function, I get plots like this:
I'm stuck, and some help would be just fine!
Thanks in advance.

Answer 1

Try with ggplot (I have changed the case value of rows 11:20 to 2):
ggplot()+
geom_density(data=testdf[testdf$case==1,], aes(age),fill='red', alpha=0.5)+
geom_density(data=testdf[testdf$case==2,], aes(age), fill='green', alpha=0.5)