使用插入符号中的ROCR包的自定义指标

Question

这是我的问题的最小例子。我想将Recall用作插入符号中的性能指标

library(caret)
set.seed(1234)

x <- matrix(rnorm(10),nrow=5,ncol=2 )
y <- factor(c("y","n","y","y","n"))


my.metric <- function (data,
                   lev = NULL,
                   model = NULL) {
  out <- ROCR::performance(ROCR::prediction(data$pred,       as.numeric(data$obs)-1,"rec"))
  names(out) <- "REC"
  out
 }

 myControl <- trainControl(summaryFunction = my.metric, method="repeatedcv", number=10, repeats=2)

 fit <- train(y=y,x=x, metric = "REC",method="gbm", trControl = myControl)

然而，我收到此错误

 Error in ROCR::prediction(data$pred, as.numeric(data$obs) - 1, "rec") : 
 Format of predictions is invalid.