在ddply中使用Summary来基于一列的max()获取整行 [英] using summarize in ddply to get entire row based on max() of one column

问题描述

df1

  primer timepoints        mean          sde
    Acan          0   1.0000000 0.000000e+00
    Acan         20   0.8758265 7.856192e-02
    Acan         40   1.0575400 4.680159e-02
    Acan         60   1.2399106 2.238616e-01
    Acan        120   1.1710685 2.085558e-02
    Acan        240   1.6430670           NA
    Acan        360   1.7747940           NA

我想要的是平均值(对于任何这些时间点)的最大值，它是对应的sde.

all I want is the max value of mean (for any of these timepoints) w/ it's corresponding sde.

   ## this will only get me the mean obviously 
   x <- ddply(x, .(primer), summarize, max = max(mean)) 

 primer        max
   Acan   1.774794


## if I were to do this I would obviously not have just the maximum values 
   x <- ddply(x. .(primer,sde), summarize, max = max(mean))

我曾经想过的一个想法可能是在df中包含时间点，然后匹配两个数据帧以获得一列sdes.然后将其绑定到df w/仅意味着.

one idea I had would be to may be to include timepoints in the df then match the two data frames to get a column of sdes. Then cbind that to the df w/ only means.

但是我觉得有一种更简单的方法可以做到这一点

But I feel as if there is an easier way to do this w/ ddply

推荐答案

如果您不必使用摘要:

ddply(x, .(primer), function(DF) DF[DF$mean == max(DF$mean),]) 

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