Plan <- read.table("https://husson.github.io/livre_exo/chap14_ex5.csv", header = TRUE, sep=";",row.names=1, encoding = "latin1") X <- model.matrix(~ X1+X2+X3+I(X1^2)+I(X2^2)+I(X3^2)+I(X1*X2)+I(X2*X3)+I(X1*X3), Plan) round(X,3) round(cor(X),3) round(solve(t(X)%*%X),3) ## Plan avec 3 points au centre Plan2 <- Plan[c(1,1,1:13),] X <- model.matrix(~ X1+X2+X3+I(X1^2)+I(X2^2)+I(X3^2)+I(X1*X2)+I(X2*X3)+I(X1*X3), Plan2) round(X,3) round(cor(X),3) round(solve(t(X)%*%X),3)