Dotplot groups on y-axis

Question

I am pretty new to R, and I have a question regarding the use of the dotplot function in the lattice package. I have multivariate data grouped by year and commodity.

Commodity   rank    Country year    tonnes
Coffee  1   Vietnam 2010    0.55
Coffee  2   Colombia    2010    0.75
Coffee  3   Brazil  2010    1.3
Coffee  4   Global Coffee   2010    2.6
Tea     5   Turkey  2010    0.2
Tea     6   Sri Lanka   2010    0.3
Tea     7   Kenya   2010    0.4
Tea     8   India   2010    1
Tea     9   China   2010    1.6
Tea     10  Global Tea  2010    3.5
Coffee  1   Vietnam 2009    0.6
Coffee  2   Brazil  2009    0.9
Coffee  3   Colombia    2009    0.9
Coffee  4   Global Coffee   2009    2.4
Tea     5   Turkey  2009    0.1
Tea     6   Sri Lanka   2009    0.1
Tea     7   Kenya   2009    0.5
Tea     8   India   2009    0.9
Tea     9   China   2009    1.7
Tea     10  Global Tea  2009    3.3

and, here's the dput() of it:

structure(list(Commodity = structure(c(1L, 1L, 1L, 1L, 2L, 2L, 
2L, 2L, 2L, 2L, 1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L, 2L, 2L), .Label = c("Coffee", 
"Tea"), class = "factor"), rank = c(1L, 2L, 3L, 4L, 5L, 6L, 7L, 
8L, 9L, 10L, 1L, 2L, 3L, 4L, 5L, 6L, 7L, 8L, 9L, 10L), Country = structure(c(10L, 
3L, 1L, 4L, 9L, 8L, 7L, 6L, 2L, 5L, 10L, 1L, 3L, 4L, 9L, 8L, 
7L, 6L, 2L, 5L), .Label = c("Brazil", "China", "Colombia", "Global Coffee", 
"Global Tea", "India", "Kenya", "Sri Lanka", "Turkey", "Vietnam"
), class = "factor"), year = c(2010L, 2010L, 2010L, 2010L, 2010L, 
2010L, 2010L, 2010L, 2010L, 2010L, 2009L, 2009L, 2009L, 2009L, 
2009L, 2009L, 2009L, 2009L, 2009L, 2009L), tonnes = c(0.55, 0.75, 
1.3, 2.6, 0.2, 0.3, 0.4, 1, 1.6, 3.5, 0.6, 0.9, 0.9, 2.4, 0.1, 
0.1, 0.5, 0.9, 1.7, 3.3)), .Names = c("Commodity", "rank", "Country", 
"year", "tonnes"), class = "data.frame", row.names = c(NA, -20L
))

Using the rank variable, I was able to produce a dotplot with a specific ordering on the y-axis, with the following code

dotplot(reorder(Country,rank)~tonnes, data=commodity, pch=21, cex=1,groups=commodity$year, 
    main="Production by country" ,
    xlab="",gcolor="black")

I would like to group the variables on the y-axis by Commodity as in the example in the link below.

_{(source: statmethods.net)}

This example uses dotchart and I've not been able to reproduce the results using dotplot. I'd be grateful for any help.

Answer 1

If you don't mind using ggplot2, this might work for you:

gg <- ggplot(data=dat, aes(x=tonnes, y=reorder(Country, rank)))
gg <- gg + geom_point(aes(color=Commodity))
gg <- gg + facet_wrap(~Commodity, ncol=1)
gg <- gg + labs(y="", title="Production by country")
gg <- gg + theme_bw()
gg <- gg + theme(legend.position="none")
gg <- gg + theme(panel.grid.major.x=element_blank())
gg <- gg + theme(panel.grid.minor.x=element_blank())
gg <- gg + theme(strip.background=element_blank())
gg

Or, you can get it more dotplot-ish by:

gg <- ggplot(data=dat, aes(x=tonnes, y=reorder(Country, rank)))
gg <- gg + geom_point(aes(color=Commodity))
gg <- gg + facet_grid(Commodity~., scales="free", space="free")
gg <- gg + labs(y="", title="Production by country")
gg <- gg + theme_bw()
gg <- gg + theme(legend.position="none")
gg <- gg + theme(panel.grid.major.x=element_blank())
gg <- gg + theme(panel.grid.minor.x=element_blank())
gg <- gg + theme(strip.background=element_blank())
gg

Or:

gg <- ggplot(data=dat, aes(x=tonnes, y=reorder(Country, rank)))
gg <- gg + geom_point(aes(color=Commodity))
gg <- gg + facet_wrap(~Commodity, ncol=1, space="free")
gg <- gg + labs(y="", title="Production by country")
gg <- gg + theme_bw()
gg <- gg + theme(legend.position="none")
gg <- gg + theme(panel.grid.major.x=element_blank())
gg <- gg + theme(panel.grid.minor.x=element_blank())
gg <- gg + theme(strip.background=element_blank())
gg