[R] Plotting LDA results

[Uwe Ligges]

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
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