Combined positive and negative stacked line plots - r

Question

I am trying to make a stacked line plot in ggplot2 with positive values stacked above the x-axis and negative values stacked separately below the x-axis. I have had success stacking each of the line types separately, but have not been able to have both on a single plot. I'm looking for some help on how I can do this, either by overlaying plots or doing something creative on a single plot.
My code below uses a simple ggplot with stacked geom_line plot. Half of the "Types" are positive values with respect to time and the other half of the "Types" are all negative values.
p <- ggplot(dataForm, aes(x=Time,y=Value,group=Type),colour=factor(Type))
p + geom_line(aes(fill = Type),position = "stack")
I have tried an alternative of specifying the positive and negative values separately without success:
p <- ggplot(dataForm, aes(x=Time,y=Value,group=Type),colour=factor(Type))
p + geom_line(data = data1,aes(fill = Type),position = "stack")
p + geom_line(data = data1,aes(fill = Type),position = "stack")
Any advice on how to do this is greatly appreciated. Thanks.

Answer 1

In the absence of a reproducible example, I adapted this example from learnr:
library(ggplot2)
library(plyr)
data = read.table(text="Time Type Value
1 a 8
2 a 10
3 a 10
4 a 5
5 a 3
1 b 9
2 b 5
3 b 7
4 b 8
5 b 3
1 c -3
2 c -1
3 c -5
4 c -4
5 c -7
1 d -11
2 d -3
3 d -9
4 d -6
5 d -6", header=TRUE)
p <- ggplot(data, aes(x=Time))
p <- p + geom_line(subset = .(Type %in% c('a', 'b')),
aes(y=Value, colour = Type),
position = 'stack')
p <- p + geom_line(subset = .(Type %in% c('c', 'd')),
aes(y=Value, colour = Type),
position = 'stack')
p
To produce this:
And, for good measure, an area chart with a horizontal line:
p <- ggplot(data, aes(x=Time))
p <- p + geom_area(subset = .(Type %in% c('a', 'b')),
aes(y=Value, fill=Type),
position = 'stack')
p <- p + geom_area(subset = .(Type %in% c('c', 'd')),
aes(y=Value, fill = Type),
position = 'stack')
p <- p + geom_hline(yintercept=0)
p