On Oct 14, 2009, at 12:24 PM, Alejo C.S. wrote:

Hi Alain, thanks for the fast response. I've the same results with iris
data, but when I use my data (mentioned in the first message),

You are apparently under the false impression that the data made it through the listserv. Read the Posting Guide to find out why that impression is false.


I have
different results.

Regards,

Alejo

2009/10/14 Alain Guillet <alain.guil...@uclouvain.be>

Hi,

I did it with

Iris <- data.frame(rbind(iris3[,,1], iris3[,,2], iris3[,,3]), Sp =
rep(c("s","c","v"), rep(50,3)))
train <- sample(1:150, 75) table(Iris$Sp[train])
z <- lda(Sp ~ ., Iris, prior = c(1,1,1)/3, subset = train)

Then I did plot(z,xlim=c(-10,10),ylim=c(-10,10)) before drawing
points(predict(z)$x,
col=palette()[predict(z)$class],xlim=c(-10,10),ylim=c(-10,10)) and all the points are superimposed. The only difference I found was the different x-
and y-axis when I drew them separately, i.e.
plot(z)
plot(predict(z)$x, col=palette()[predict(z)$class])


Alain



Alejo C.S. wrote:

I'm confused on how is the right way to plot a discriminant analysis made
by
lda function (MASS package).
(I had attached my data fro reproduction). When I plot a lda object :

X <- read.table("data", header=T)

lda_analysis <- lda(formula(X), data=X)

plot(lda_analysis)

#the above plot is completely different to:

plot(predict(lda_analysis)$x, col=palette()[predict(lda_analysis) $class])

that should be the same graph than the first?

In the second case, I use predict function to obtain the LD1 and LD2
coordinates of lda_analysis (predict(lda_analysis)$x) and it's respective class (predict(lda_analysis)$class), but it seems that the classes are
different:

table(X$G3, predict(lda_analysis)$class)

      B    G   M
B  29    0    3
G    0  26   2
M   4    0  46


any clues?
Regards,
------------------------------------------------------------------------

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--
Alain Guillet
Statistician and Computer Scientist

SMCS - Institut de statistique - Université catholique de Louvain
Bureau c.316
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