如何计算数据框所有列的平均值[重复]

Question

我有一个数据框，我想计算所有列的平均值并将其保存到一个新的数据框中。我找到了这个解决方案calculate the mean for each column of a matrix in R 但是，这仅适用于矩阵而不是数据框

structure(list(TotFlArea = c(1232, 596, 708, 1052, 716), logg_weighted_assess = c(13.7765298160156, 
13.1822275291412, 13.328376420438, 13.3076293132057, 13.5164823091252
), TypeDwel1.2.Duplex = c(0, 0, 0, 0, 0), TypeDwelApartment.Condo = c(0, 
1, 1, 1, 1), TypeDwelTownhouse = c(1, 0, 0, 0, 0), Age_new.70 = c(0, 
0, 0, 0, 0), Age_new0.1 = c(0, 0, 0, 0, 0), Age_new16.40 = c(1, 
1, 0, 1, 0), Age_new2.5 = c(0, 0, 0, 0, 0), Age_new41.70 = c(0, 
0, 0, 0, 0), Age_new6.15 = c(0, 0, 1, 0, 1), LandFreehold = c(1, 
1, 1, 0, 1), LandLeasehold.prepaid = c(0, 0, 0, 1, 0), LandOthers = c(0, 
0, 0, 0, 0), cluster_K_mean.1 = c(0, 0, 0, 0, 0)), row.names = c("1", 
"2", "3", "4", "5"), class = "data.frame")

你能告诉我怎么做吗？

注意：我的数据框可以有 NA 值，应该从平均值计算中排除

Answer 1

正如@akrun 指出的那样。也是另一种选择

apply(df, 2, mean)

其中2 表示按列，1 表示按行。

但是，除了它的灵活性（例如从平均值更改为模式或仅应用于选定的列apply(df[,c('a', 'b')], 2, mean)）之外，下面还显示了使用apply 的缺点（在速度方面）

library(data.table)
library(microbenchmark)

# dummy data
x <- 1e7
df <- data.table(a = 1:x )
y <- letters[2:10]
df[, (y) := lapply(2:10, \(i) a+i)]

# benchmark
z <- 
microbenchmark(colMeans = {colMeans(df)}
               , apply = {apply(df, 2, mean)}
               , times = 30
               )

plot(z)