给定列名，数据框中列的均值 [英] Mean of a column in a data frame, given the column's name

问题描述

我在一个必须编写的大函数中.在最后一部分中，我必须计算数据帧中一列的平均值.我正在处理的列的名称作为该函数的参数给出.

I'm inside a big function I have to write. In the last part I have to calculate the mean of a column in a data frame. The name of the column I am operating on is given as an argument to the function.

推荐答案

我认为您在问如何根据给定的列名计算数据框中变量的均值.有两种典型的方法，一种使用[[进行索引，另一种使用[进行索引:

I think you're asking how to compute the mean of a variable in a data frame, given the name of the column. There are two typical approaches to doing this, one indexing with [[ and the other indexing with [:

data(iris)
mean(iris[["Petal.Length"]])
# [1] 3.758
mean(iris[,"Petal.Length"])
# [1] 3.758
mean(iris[["Sepal.Width"]])
# [1] 3.057333
mean(iris[,"Sepal.Width"])
# [1] 3.057333

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