小编Tho*_*sen的帖子

如何contour用ggplot2 绘制等效的(基数R)？以下是线性判别函数分析的示例:

require(MASS)
iris.lda<-lda(Species ~ Sepal.Length + Sepal.Width + Petal.Length + Petal.Width, data =    iris)
datPred<-data.frame(Species=predict(iris.lda)$class,predict(iris.lda)$x) #create data.frame

#Base R plot
eqscplot(datPred[,2],datPred[,3],pch=as.double(datPred[,1]),col=as.double(datPred[,1])+1) 

#Create decision boundaries
iris.lda2 <- lda(datPred[,2:3], datPred[,1])
x <- seq(min(datPred[,2]), max(datPred[,2]), length.out=30)
y <- seq(min(datPred[,3]), max(datPred[,3]), length.out=30)
Xcon <- matrix(c(rep(x,length(y)),
             rep(y, rep(length(x), length(y)))),,2) #Set all possible pairs of x and y  on a grid

iris.pr1 <- predict(iris.lda2, Xcon)$post[, c("setosa","versicolor")] %*% c(1,1)    #posterior probabilities of a point belonging to each class 
contour(x, y, matrix(iris.pr1, length(x), length(y)), 
    levels=0.5, …