extract hyperplan from e1071 model
Hi, Please don't forget to copy R-help on your reply - other people are likely to have more insight. My understanding is that you want to replicate the shaded polygons produced by plot.svm on your own plot. That's why I suggested you first try add=TRUE, and if that doesn't work, then look at the code for plot.svm so you can see how the predicted values are calculated on a grid to be plotted. R is open source - you can extract the section from that function that does what you want, and make your own code to add it to another plot. I have no idea what "the tutorial" is; I suggested two things you could try based on the help and my understanding of R. Sarah
On Thu, Dec 20, 2018 at 9:07 AM Luigi Marongiu <marongiu.luigi at gmail.com> wrote:
Dear Sarah, I have looked at the tutorial but I did not find what I was looking for. Essentially, I would like to extract the data that make the hyperplane (it should be a matrix of X,Y value, for a bidimensional plane, I guess) so I can plot a line in another plot. I tried with model$SV but it is not the right one. Luigi On Thu, Dec 20, 2018 at 2:59 PM Sarah Goslee <sarah.goslee at gmail.com> wrote:
Hi, According to the help for svm, which you probably should have started with, SV contains the support vectors, and index contains the position of the support vectors in the data matrix. As for plotting, plot.svm lets you pass additional options to plot so that you can customize the plot to your tastes. I'm not sure if add=TRUE is a useful option there, but you should try it. If that doesn't meet your needs, R is open source - you can easily look at the code for plot.svm and see what you need (basically the predicted values on agrid, if I'm understanding your goal correctly). Sarah On Thu, Dec 20, 2018 at 5:16 AM Luigi Marongiu <marongiu.luigi at gmail.com> wrote:
Dear all, I am using the package e1071 for modeling SVM. I obtain a model from the data and I can plot the results; the plot shows the support vectors (as 'X's) and the shaded areas as it should be. However, I don't like the plot generated from the model and I would like instead to have more control upon the plotting; in particular, I would like to draw the hyperplane on plots I have already made from the data available. Is there a way to extract the values that are used to draw the hyperplane? That is: plot(model) -- where model is obtained from svm() -- draws an area in blue and one in red based on some values provided by model; can I get these values so I can plot a line in a pre-existing plot? Also, it is possible to extract the positions of the support vectors? The names of the model generated by svm() are:
names(mod)
[1] "call" "type" "kernel" "cost" [5] "degree" "gamma" "coef0" "nu" [9] "epsilon" "sparse" "scaled" "x.scale" [13] "y.scale" "nclasses" "levels" "tot.nSV" [17] "nSV" "labels" "SV" "index" [21] "rho" "compprob" "probA" "probB" [25] "sigma" "coefs" "na.action" "fitted" [29] "decision.values" "terms" Which one should I look at? Thank you -- Best regards, Luigi
Sarah Goslee (she/her) http://www.numberwright.com