假设我有一个逻辑数组:
dimensions = c(10,100,200,300)
x = runif(prod(dimensions))>0.3
dim(x) = dimensions
是否有更快的方法来获得结果:
y = colMeans(apply(x,2:4,all))
?
应用非常慢,这个用例非常简单,因此我徘徊了...
使用colSums
:
system.time(
y <- colMeans(apply(x,2:4,all))
)
# user system elapsed
#6.916 0.058 6.978
system.time(
z <- colMeans(colSums(x, 1) == dim(x)[1])
)
# user system elapsed
#0.117 0.000 0.117
identical(y, z)
#[1] TRUE