根据两列查找唯一组合并计算平均值 [英] Find unique combinations based on two columns and calculate the mean

问题描述

我在 R 中有一个问题，我似乎无法解决.

I have a problem in R, which I can't seem to solve.

我有以下数据框:

图片 1

我想:

1. 找到物种"和影响"列的独特组合
2. 报告属于这个独特组合的浓度
3. 如果这种独特的组合出现多次，计算平均浓度

并希望获得以下数据框:

And would like to get the following dataframe:

图片 2

我尝试了下一个脚本来获得独特的组合:

I have tried next script to get the unique combinations:

UniqueCombinations <- Data[!duplicated(Data[,1:2]),]

UniqueCombinations <- Data[!duplicated(Data[,1:2]),]

但不知道如何从那里开始.

but don't know how to proceed from there.

预先感谢您的回答！

蒂娜

推荐答案

请尝试以下操作(感谢 Brandon Bertelsen 的精彩评论):

Try the following (Thanks Brandon Bertelsen for nice comment):

创建数据:

foo = data.frame(Species=c(rep("A",4),"B",rep("C",3),"D","D"), 
                 Effect=c(rep("Reproduction",3), rep("Growth",2),
                          "Reproduction", rep("Mortality",2), rep("Growth",2)), 
                 Concentration=c(1.2,1.4,1.3,1.5,1.6,1.2,1.1,1,1.3,1.4))

使用很棒的包 plyr 来一点魔法:)

Using great package plyr for a bit of magic :)

library(plyr)
ddply(foo, .(Species,Effect), function(x) mean(x[,"Concentration"]))

这是一个更复杂但更干净的版本(再次感谢 Brandon Bertelsen):

And this is a bit more complicated, but cleaner version (Thanks again to Brandon Bertelsen):

ddply(foo, .(Species,Effect), summarize, mean=mean(Concentration))

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