R打印矢量的一個元素

Question

這是一個編程問題。我不知道如何打印出一個矢量的一個元素。我的代碼如下：

# 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

如果我明白你在問什麼，這應該工作。這是一個簡單的例子。

a <- c(1,2,3,3) 
thresh <- c(1,2,3,4) 

# run at command line 
> thresh[a==max(a)] 
    [1] 3 4