[R] Plotting LDA results

Uwe Ligges ligges at statistik.tu-dortmund.de
Wed Jul 25 15:14:40 CEST 2012

On 25.07.2012 13:52, Meffy wrote:
> Dear Users!
> I think I still have some problems in understanding LDA and the methods of
> plotting the results.
> The case is the following: I'm having a dataset containing two classes where
> each datapoint has 19 dimensions. Training with lda(...) works fine, and I'm
> getting 19 LD coefficients. So far so good. Now I want to visualize the
> result, and here is where my simple knowledge ends. What I simply want to do
> is doing a scatterplot on two dimensions and then plotting the projected
> hyperplane in order to see the dividing line. The scatterplot I'm doing with
> plot(class1[1:100,1], class1[1:100,2])
> points(class2[1:100,1], class2[1:100,2])
> but now I face with the problem of determining the intercept for abline(...)
> (the slope should be -LD[1]/LD[2] I think...).

The scatterplot shows a projection on the first two linear discriminant 
components, the histogram is the projection on the first component only.

> What I really don't understand is the result of plot.lda(...). As a result
> it gives two histograms, each one for one class. So which distributions are
> shown there?
> And why does it only plot a scatterplot when I have three
> classes?

If you have two classes, there will only be one component. No chance two 
invent a second dimension.

Uwe Ligges

> Thank you very much in advance!
> Greetings, Matthias
> --
> View this message in context: http://r.789695.n4.nabble.com/Plotting-LDA-results-tp4637766.html
> Sent from the R help mailing list archive at Nabble.com.
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

More information about the R-help mailing list