r - For循环交叉验证R
问题描述
我正在尝试创建一个循环(执行 10 次)以重复交叉验证以评估 4 个模型的预测性能,然后我必须计算我的性能的平均值。我必须承认我是 R 的新手,我正在为这个简单的任务而苦苦挣扎。我首先创建了我的公式来交叉验证我的模型。
loss.mse <- function(fit, df, y, transf){
y_pred <- transf(predict(fit, df))
out <- (y - y_pred)^2
return(mean(out))
}
loss.mae <- function(fit, df, y, transf){
y_pred <- transf(predict(fit, df))
out <- abs(y - y_pred)
return(mean(out))
}
validate.cv <- function(data, folds, model_fn, y_var,
transf = identity, seed)
{
set.seed(seed)
fold_id <- sample(rep(1:folds, length.out = nrow(data)))
out.mse <- out.mae <- numeric(folds)
for(test in 1:folds){
data_test <- subset(data, fold_id == test)
data_train <- subset(data, fold_id != test)
fit <- model_fn(data_train)
y_test <- y_var[fold_id == test]
out.mse[test] <- loss.mse(fit, data_test, y_test, transf)
out.mae[test] <- loss.mae(fit, data_test, y_test, transf)
}
return(list(MAE = mean(out.mae), MSE = out.mse,
RMSE = sqrt(mean(out.mse))))
然后我命名了我的模型并交叉验证了它们,但我不知道如何获得我的 10 次循环!
model_lm <- function(data) lm(StockPrice ~., data)
model_step <- function(data) step(lm(StockPrice ~., data), trace = 0)
model_rpart <- function(data)
{
set.seed(1234)
mod.rpart <- rpart(StockPrice ~ ., data, cp = 0.0001, model = TRUE)
cp.select <- function(big.tree) {
min.x <- which.min(big.tree$cptable[, 4])
for(i in 1:nrow(big.tree$cptable)) {
if(big.tree$cptable[i, 4] <
(big.tree$cptable[min.x, 4] + big.tree$cptable[min.x, 5]))
return(big.tree$cptable[i, 1])
}
}
mod.rpart.prune <- prune(mod.rpart, cp = cp.select(mod.rpart))
return(mod.rpart.prune)
}
model_step_gam <- function(data)
{
mod <- model_step(data)
predictors <- all.vars(terms(mod))[-1]
f <- as.formula(
paste("StockPrice",
paste(paste("s(",predictors, ")"), collapse = " + "),
sep = " ~ "))
mod_gam <- gam(f, data = data)
seed<-1234
m.log.full <-validate.cv(log.Finance, 10, model_lm, Finance$StockPrice,exp, seed)
m.log.step <-validate.cv(log.Finance, 10, model_step, Finance$StockPrice,exp, seed)
m.log.rpart <-validate.cv(log.Finance, 10, model_rpart, Finance$StockPrice,exp, seed)
m.log.gam <-validate.cv(log.Finance, 10, model_step_gam, Finance$StockPrice,exp, seed)
mat.test <-data.frame(Model =c("Full (log)","Step (log)","CART (log)", "Step GAM (log)"),
RMSE =c(m.log.full$RMSE, m.log.step$RMSE,m.log.rpart$RMSE, m.log.gam$RMSE),
MAE =c(m.log.full$MAE, m.log.step$MAE, m.log.rpart$MAE,m.log.gam$MAE))
print(mat.test)
如果您有任何想法,我很乐意尝试。预先感谢您的帮助 :)
解决方案
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