Finally, I did not find the detail of the “R_svmpredict” function that may be a C program but applying the function named “svmpred” in the svminternals.pdf document I solved my problem.

Thank you and best regards, Benoit.

De : Sarah Goslee <

[hidden email]>

Envoyé : mercredi 28 août 2019 12:50

À : PELE Benoît (Acoss) <

[hidden email]>

Cc :

[hidden email]
Objet : Re: [R] SVM - calculating values problem

You could download the package code from CRAN and look yourself at what the predict function is doing.

Sarah

On Wed, Aug 28, 2019 at 6:35 AM PELE Benoît (Acoss) <

[hidden email]<mailto:

[hidden email]>> wrote:

Hello everybody,

That is the first time that I am working on a SVM modeling and I would like to calculate by myself the result values from the SVM for each line of my database (named x_appr_svm).

First I tested a linear SVM model using the e1071 package and to calculate the individual results by myself I did the next things :

Retrieving the model coefficients : coef_svm<-t(svm$coefs) %*% x_appr_svm[svm$index,]

Calculating the values for each line : p2<-x_appr_svm %*% t(coef_svm) - svm$rho

Using the predict function to compare : p1<-attr(predict(object=svm, newdata=x_appr_svm, decision.values=T), "decision.values")

--> p1 and p2 are the same.

Next I tested a polynomial SVM model using the same package and the same method knowing that the model parameters are :

degree=2, gamma=0.02, coef0=0.01

The calculation of the individual values becomes (I guess) : p2<-(0.02*x_appr_svm %*% t(coef_svm)+0.01)^2-svm$rho

--> p1 and p2 are really different!

Despite of my searching, I do not understand why or where is the problem in my second p2 formula. Do you see the mistake?

Thank you for your help and have a good day, Benoit (France).

[[alternative HTML version deleted]]

______________________________________________

[hidden email]<mailto:

[hidden email]> mailing list -- To UNSUBSCRIBE and more, see

https://stat.ethz.ch/mailman/listinfo/r-helpPLEASE do read the posting guide

http://www.R-project.org/posting-guide.htmland provide commented, minimal, self-contained, reproducible code.

--

Sarah Goslee (she/her)

http://www.sarahgoslee.com [[alternative HTML version deleted]]

______________________________________________

[hidden email] mailing list -- To UNSUBSCRIBE and more, see

https://stat.ethz.ch/mailman/listinfo/r-helpPLEASE do read the posting guide

http://www.R-project.org/posting-guide.htmland provide commented, minimal, self-contained, reproducible code.