R打印向量的一个元素

Question

这是一个编程问题。我不明白如何打印出向量的1个元素。我的代码如下：

# creating a range of values to test for accuracy
thresh=seq(0,1,by=0.05)
acc = matrix(0,1,20)
# computing accuracy for different threshold values from 0 to 1 step by 0.05
for (i in 1:21){
  matrix = confusion.matrix(obs,pred,threshold=thresh[i])
  acc[i]=(matrix[1,1]+matrix[2,2])/nrow(test)
  acc[i]}
max(acc)
library(nnet)
which.is.max(acc)
acc
#Q how can I print only thresh[12] the first max(acc)? 
   there may be more than one thresh with the max(acc).
print(thresh)

???

Answer 1

如果我了解您的要求，这应该有效。这是一个简单的例子。

a <- c(1,2,3,3)
thresh <- c(1,2,3,4)
# run at command line
> thresh[a==max(a)]
  [1] 3 4