r - 具有 NA 的数据框列表的元素明智平均值

Question

我有一个数据帧 x 的列表，我想找到数据帧中每个元素的平均值。我在网上找到了一个由 Dimitris Rizopoulos 提供的优雅解决方案。

x.mean = Reduce("+", x) / length(x) 

但是，当数据帧包含 NA 时，这实际上不起作用。有没有什么好方法可以做到这一点？

Answer 1

Here is an approach that uses data.table

The steps are (1) coerce each data.frame [element] in x to data.table, with a column (called rn) identifying the rownames. (2) on the large data.table, by rowname calculate the mean of each column (with na.rm = TRUE dealing with NA values). (3) remove the rn column

library(data.table)


results <- rbindlist(lapply(x,data.table, keep.rownames = TRUE))[,
                     lapply(.SD, mean,na.rm = TRUE),by=rn][,rn := NULL]

an alternative would be to coerce to matrix, "simplify" to a 3-dimensional array then apply a mean over the appropriate margins

    # for example

    results <- as.data.frame(apply(simplify2array(lapply(x, as.matrix)),1:2,mean, na.rm = TRUE))

Answer 2

我更喜欢@mnel 的解决方案，但作为一个教育练习，您可以修改表达式以使用NA值，同时保持相同类型的逻辑：

Reduce(function(y,z) {y[is.na(y)] <- 0; z[is.na(z)] <- 0; y + z}, x) /
  Reduce('+', lapply(x, function(y) !is.na(y)))