从R中的数据框中提取原始和重复结果 [英] Extract original and duplicate result(s) from a data frame in R

问题描述

我使用重复的结果来估计化学分析的测量不确定度.当我从实验室数据库中提取数据时，它主要由单一结果组成，但有些样品进行了两次测试，有些样品进行了两次以上(我看过多达12次).我想放弃所有单个分析，只保留重复的结果，但包括原始结果.

I use duplicate results to estimate the measurement uncertainty for chemical analyses. When I extract data from the laboratory database it consists largely of single results but with some samples tested twice, some more than twice (I have seen up to 12). I want to discard all the single analyses and just retain the duplicated results, but including the original result.

通过重复样本共有的样本编号来识别样本.

The samples are identified by a sample number that is common to the duplicate samples.

我可以使用duplicated()提取重复项，但是如何保留第一个结果呢?

I can pull out the duplicates using duplicated() but how to I retain the first result as well?

谢谢.

推荐答案

> dat <- data.frame(
    id = sample(1:5, 10, replace = TRUE),
    x = rnorm(10)
    )

> dat
##    id          x
## 1   1  0.7060512
## 2   4  0.6804117
## 3   2  0.2395902
## 4   2  1.5352574
## 5   1  0.2376593
## 6   4  0.8019506
## 7   1 -1.0506505
## 8   5  1.0554555
## 9   3  0.3637685
## 10  5 -0.8404215
> dat[duplicated(dat$id) | duplicated(dat$id, fromLast = TRUE),]
##    id          x
## 1   1  0.7060512
## 2   4  0.6804117
## 3   2  0.2395902
## 4   2  1.5352574
## 5   1  0.2376593
## 6   4  0.8019506
## 7   1 -1.0506505
## 8   5  1.0554555
## 10  5 -0.8404215

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