按比例汇总 [英] Summary of proportions by group

问题描述

什么是用于按子组计算比例的最佳工具/包？我以为我可以尝试这样的事情：

What would be the best tool/package to use to calculate proportions by subgroups? I thought I could try something like this:

data(mtcars)
library(plyr)
ddply(mtcars, .(cyl), transform, Pct = gear/length(gear))

但是输出不是我想要的，因为我想要一些等于 cyl 的行数。即使将其更改为总结我仍然遇到同样的问题。

But the output is not what I want, as I would want something with a number of rows equal to cyl. Even if change it to summarise i still get the same problem.

我对其他软件包开放，但我认为 plyr 将是最好的，因为我最终会围绕这个建立一个功能。任何想法？

I am open to other packages, but I thought plyr would be best as I would eventually like to build a function around this. Any ideas?

感谢任何帮助，只需解决这样的基本问题。

I'd appreciate any help just solving a basic problem like this.

推荐答案

要获取组内的频率：

library(dplyr)
mtcars %>% count(cyl, gear) %>% mutate(Freq = n/sum(n))
# Source: local data frame [8 x 4]
# Groups: cyl [3]
# 
#     cyl  gear     n       Freq
#   (dbl) (dbl) (int)      (dbl)
# 1     4     3     1 0.09090909
# 2     4     4     8 0.72727273
# 3     4     5     2 0.18181818
# 4     6     3     2 0.28571429
# 5     6     4     4 0.57142857
# 6     6     5     1 0.14285714
# 7     8     3    12 0.85714286
# 8     8     5     2 0.14285714

或等价于

mtcars %>% group_by(cyl, gear) %>% summarise(n = n()) %>% mutate(Freq = n/sum(n))

仔细分析每个阶段的分组，或者你的nu mbers将关闭。

Careful of what the grouping is at each stage, or your numbers will be off.

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