在函数中使用ddply

问题描述

我正在尝试在其中使用ddply创建一个函数.但是我不能上班.这是一个重现我所得到的虚拟例子.这有什么事此错误吗?

I'm trying to make a function using ddply inside of it. However I can't get to work. This is a dummy example reproducing what I get. Does this have anything to do this bug?

library(ggplot2)
data(diamonds)

foo <- function(data, fac1, fac2, bar) {
  res <- ddply(data, .(fac1, fac2), mean(bar))
  res
}

foo(diamonds, "color", "cut", "price")

推荐答案

我不认为这是一个错误. ddply需要一个函数的名称，而mean(bar)并未真正提供该函数的名称.您需要编写一个完整的函数来计算您想要的均值:

I don't believe this is a bug. ddply expects the name of a function, which you haven't really supplied with mean(bar). You need to write a complete function that calculates the mean you'd like:

foo <- function(data, fac1, fac2, bar) {
  res <- ddply(data, c(fac1, fac2), function(x,ind){
                                     mean(x[,ind]},bar)
  res
}

此外，您不应该将字符串传递给.()，因此我将其更改为c()，以便可以将函数参数直接传递给ddply.

Also, you shouldn't pass strings to .(), so I changed that to c(), so that you can pass the function arguments directly to ddply.

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