汇总方法对缺失值(NA)的处理方式不同 [英] aggregate methods treat missing values (NA) differently

问题描述

这是一个缺少值的简单数据框:

Here's a simple data frame with a missing value:

M = data.frame( Name = c('name', 'name'), Col1 = c(NA, 1) , Col2 = c(1, 1))
#   Name Col1 Col2
# 1 name   NA    1
# 2 name    1    1

当我使用formula方法按组(名称")使用aggregate至sum变量时:

When I use aggregate to sum variables by group ('Name') using the formula method:

aggregate(. ~ Name, M, FUN = sum, na.rm = TRUE)

结果是:

# RowName Col1 Col2
#    name    1    1

因此具有NA的整个第一行将被忽略.但是，如果使用"non- formula"，规格:

So the entire first row, which have an NA, is ignored. But if use the "non-formula" specification:

aggregate(M[, 2:3], by = list(M$Name), FUN = sum, na.rm = TRUE)

结果是:

# Group.1 Col1 Col2
#    name    1    2

这里只有(1,1)项被忽略.

Here only the (1,1) entry is ignored.

这在我的一个代码中引起了严重的调试麻烦，因为我认为这两个调用是等效的. formula进入方法被不同地对待是有充分的理由吗?

This caused a major debugging headache in one of my codes, since I thought these two calls were equivalent. Is there a good reason why the formula entry method is treated differently?

谢谢.

推荐答案

很好的问题，但是我认为这不应该引起 major 调试的麻烦，因为在很多情况下它都记录得很清楚.在aggregate的手册页中放置.

Good question, but in my opinion, this shouldn't have caused a major debugging headache because it is documented quite clearly in multiple places in the manual page for aggregate.

首先，在用法"部分:

## S3 method for class 'formula'
aggregate(formula, data, FUN, ...,
          subset, na.action = na.omit)

稍后，在说明中:

na.action:该函数指示当数据包含NA值时应发生的情况.默认设置是忽略给定变量中的缺失值.

na.action: a function which indicates what should happen when the data contain NA values. The default is to ignore missing values in the given variables.

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我无法回答为什么公式模式的编写方式有所不同-这是函数作者必须回答的一些内容--但是使用以上信息，您可能可以使用以下内容:

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I can't answer why the formula mode was written differently---that's something the function authors would have to answer---but using the above information, you can probably use the following:

aggregate(.~Name, M, FUN=sum, na.rm=TRUE, na.action=NULL)
#   Name Col1 Col2
# 1 name    1    2

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