计算数据帧中的列的百分比 - “分组”按列 [英] Calculate the percentages of a column in a data frame - "grouped" by column

问题描述

我是一名R初学者，来到这一点，我需要计算数据框中的值的百分比，但是经常会以另一个列值分组。

I am an R beginner and came to the point, where I need the possibility to calculate percentages of values in a data frame, but "grouped" by an other column value, quite often.

我有一个包含mediatype，version，collection（= year）和count（今年）的大约1000行的数据框。我可以过滤它们，只得到一个特定的媒体：

I have a data frame with around 1000 rows, containing mediatype, version, collection (= year) and count (for this year). I can filter them, to get only a specific mediatye:

trSpdf <- trS[trS$Mediatype == 'application/pdf',]

并获得以下示例性输出：

and get the following exemplary output:

> trSpdf 

        Mediatype Version Collection      Count
39 application/pdf      -1     co2008         2.0
40 application/pdf      -1     co2009         5.0
43 application/pdf       1     co2008         1.0
44 application/pdf       1     co2009         1.0
48 application/pdf     1.1     co2008        16.0
52 application/pdf     1.2     co2008        20.0
53 application/pdf     1.2     co2009        90.0
... (continuing) ...

我想要的是计算每个集合的每个版本的百分比=年）与本集合中的所有版本相比，因此在此示例中，结果应为：

What I want, is to calculate the percentage of each version for each collection (= year) compared to all versions in this collection, so for this example the result should be:

5.12% of all versions in co2008 were version -1 (2.0 / total sum for co2008)
2.56% of all versions in co2008 were version 1 (1.0 / total sum for co2008)
...
93,75% of all versions in co2009 were version 1.2 (90.0 / total sum for co2009)
...

提前感谢我如何解决这个问题的任何答案。

Thanks in advance for any answers on how I could solve this.

推荐答案

首先，使用 ave 添加一列，列出每个 Mediatype 和 Collection ：

First, use ave to add a column giving the total count per Mediatype and Collection:

trS <- transform(trS, Tot.Count = ave(Count, Mediatype, Collection, FUN = sum))

然后，很明显如何计算百分比：

Then, it is easy pretty obvious how to compute the percentage:

trS <- transform(trS, percentage = 100 * Count/Tot.Count)

或者如果你想要它很好地格式化（例如5.13％）然后使用 sprintf ：

Or if you want it nicely formatted (e.g. "5.13%") then use sprintf:

trS <- transform(trS, percentage = paste0(sprintf("%.2f", 100 * Count/Tot.Count),
                                          "%"))

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