DEA -- Extract the Frontier and ggplot2

[Lorenzo Isella]

Dear All,
Please consider the code at the end of the email.
Everything is fine in this little example, just I do not know how to
extract the DEA frontier (solid line in the plot).
The reason is that I want to reproduce a more complicated DEA frontier
plot using ggplot2 and I need to understand how I can extract the
frontier data. Alternatively: can anyone reproduce the same plot with ggplot2?
Many thanks

Lorenzo

###########################################à



library(Benchmarking) # load the Benchmarking library

x <- matrix(c(20, 40, 40, 60, 70, 50),ncol=1) #define inputs
y <- matrix(c(20, 30, 50, 40, 60, 20),ncol=1) #define outputs

e_vrs <- dea(x,y, RTS="vrs", ORIENTATION="in")#solve LP problem
eff_dea <- eff(e_vrs) #select efficiency scores from the results in e




dd <- as.data.frame(cbind(x,y))

names(dd) <- c("Input", "Output")
dd$Firm <- LETTERS[1:length(x)]

dd$Input <- as.integer(dd$Input)
dd$Output <- as.integer(dd$Output)

pdf("dea-frontier-vrs.pdf")
par( mar = c(4.5,5, 1, 1) + 0.1)
dea.plot(x,y,RTS="vrs",ORIENTATION="in",txt=LETTERS[1:length(x)],lty="dashed",
xlab="Input", ylab="Output", fex=2,
cex=2,cex.lab=2,cex.axis=2)
dea.plot.frontier(x,y, RTS="vrs", add=T)
text(10,60, "VRS", cex=2)
dev.off()

[Lorenzo Isella]

Hello,
Thanks for your suggestion, but it is does not help me much.
Indeed, in this case where RTS="vrs", things are easy as you say.
However, try for instance to change the technology assumption
(e.g. replace it with RTS="drs" everywhere in my script) and you'll
see that things are not that simple.
I really need a way to extract the frontier -- it is plotted, so it is
calculated and it has to be buried somewhere in the package, just I do
not know where.
Cheers

Lorenzo

On Tue, Aug 02, 2016 at 09:05:15AM +0000, Jose Iparraguirre wrote:
>Lorenzo,
>
>dea.plot plots the vectors x and y, which you already have:
>data.frame(x,y)
> x y
>1 20 20
>2 40 30
>3 40 50
>4 60 40
>5 70 60
>6 50 20
>
>dea.plot.frontier plots the highest values of y for each value of x. Therefore, for x=20, the plot goes through y=20 but for X=40, where you have Y=30 and Y=50, the plot goes through the latter.
>
>Others in the list may give you an easier and better answer, but it's not difficult to plot all the X and Y in a scatterplot in ggplot and then to add a line along the highest values of Y per each X.
>
>I'm assuming you want an input orientation as in your example, of course.
>
>Hope it helps,
>
>José
>
>
>Prof. José Iparraguirre
>Chief Economist
>Age UK
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[Roman Luštrik]

Hi,

this is not really a ggplot2 issue, but here goes.

If you look at the source code of the Benchmarking package (here) you will notice that the function is not very explicit about what to return - so the returned thing is actually a plotting line (lines()). What you could do is fork the repository, add your own return statement to include the `hpts` which could be used to find the correct values in `x` (see for example here how plotting is done).

After you have the formed repository ready (and pushed to your account), you can install it through devtools::install_github("yourname/Benchmarking"). Blesssed thee, open source.

Cheers,

Roman

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