Creating Area Chart in R from xtabs Data Frame - r

Question

I have a data frame that I created using xtabs.
My goal is to create an area graph / sand chart using this data frame, I'm just not entirely sure how to declare the axes.
vg <- read.csv("vgdata.csv")
df <- data.frame(vg)
graph <- xtabs(Sales ~ Year + Genre, df)
print(graph)
Output:
Genre
Year Action RPG Shooter
2005 3 2 2
2006 1 1 3
2007 3 3 4
2008 1 5 8
2009 4 7 7
2010 4 5 2
Typically I would use Sales, Genre, Year, etc as variables of my graph, but these don't exist because of how it was created using xtabs. I simply have graph as a defined variable.
I would like to have the years on the x axis and the sales data on the y axis with the genre being labels. I'm hoping there is an easy way to do this with the format I already have. The reason I chose xtabs is because I had several video game titles under action, RPG, and shooter for each year and it was a convenient way to sum them to get a data frame of total sales per year.

Answer 1

Here are a couple of possible ways you can plot your results. For this example I'm using data from your last SO question.
Assuming you use xtabs as described:
result <- xtabs(Sales ~ Year + Genre, df)
You can convert to a data frame:
plot_data <- as.data.frame(result)
plot_data
Year Genre Freq
1 2005 Action 3
2 2006 Action 0
3 2007 Action 1
4 2005 RPG 0
5 2006 RPG 4
6 2007 RPG 2
7 2005 Shooter 3
8 2006 Shooter 0
9 2007 Shooter 3
For the area plot, you can make Year numeric instead of a factor for use on the x axis:
plot_data$Year <- as.numeric(as.character(plot_data$Year))
Then plot with geom_area:
library(ggplot2)
ggplot(plot_data, aes(x = Year, y = Freq, fill = Genre)) +
geom_area() +
scale_x_continuous(breaks = 2005:2007)
Plot
Data
df <- structure(list(Name = 1:8, Year = c(2005L, 2005L, 2005L, 2006L,
2006L, 2007L, 2007L, 2007L), Genre = c("Action", "Action", "Shooter",
"RPG", "RPG", "Action", "Shooter", "RPG"), Sales = c(1L, 2L,
3L, 2L, 2L, 1L, 3L, 2L)), class = "data.frame", row.names = c(NA,
-8L))