问题 In this example (https://gist.github.com/thigm85/8424654) LDA was examined vs. PCA on iris dataset. How can I also do LDA on the PCA results (PCA-LDA) ? Code: require(MASS) require(ggplot2) require(scales) require(gridExtra) pca <- prcomp(iris[,-5], center = TRUE, scale. = TRUE) prop.pca = pca$sdev^2/sum(pca$sdev^2) lda <- lda(Species ~ ., iris, prior = c(1,1,1)/3) prop.lda = lda$svd^2/sum(lda$svd^2) plda <- predict(object = lda, newdata = iris) dataset = data.frame(species = iris[,"Species"]