我正在用观察 test_idxs 填充分布 testa
test_idxs <- matrix(sample(c(1,2,3), 300000, repl=T), ncol=3)
testa_for_looped <- array(0, c(3,3,3))
testa_vectorized <- array(0, c(3,3,3))
system.time( for (i in 1:nrow(test_idxs)) { testa_for_looped[rbind(test_idxs[i,])] <- testa_for_looped[rbind(test_idxs[i,])] + 1 } ) ## slower
system.time( testa_vectorized[test_idxs] <- testa_vectorized[test_idxs] + 1 ) ### faster
sum(testa_for_looped) ### right
sum(testa_vectorized) ### wrong
矢量化解决方案更快，但是这个解决方案已经坏了，而且我提出的所有解决方案都比 for 循环慢。你会怎么做？