在`dplyr`输出中添加行 [英] Adding rows in `dplyr` output
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问题描述
在传统的 plyr
中,返回的行自动添加到输出,即使它们超过了该分组的输入行数:
In traditional plyr
, returned rows are added automagically to the output even if they exceed the number of input rows for that grouping:
set.seed(1)
dat <- data.frame(x=runif(10),g=rep(letters[1:5],each=2))
> ddply( dat, .(g), function(df) df[c(1,1,1,2),] )
x g
1 0.26550866 a
2 0.26550866 a
3 0.26550866 a
4 0.37212390 a
5 0.57285336 b
6 0.57285336 b
7 0.57285336 b
8 0.90820779 b
9 0.20168193 c
10 0.20168193 c
11 0.20168193 c
12 0.89838968 c
13 0.94467527 d
14 0.94467527 d
15 0.94467527 d
16 0.66079779 d
17 0.62911404 e
18 0.62911404 e
19 0.62911404 e
20 0.06178627 e
我不知道如何在 dplyr
中做同样的事情。一些尝试:
I cannot figure out how to do the same in dplyr
. Some attempts:
dat %>% group_by(g) %>% summarise( xbar = mean(x) )
> dat %>% group_by(g) %>% summarise( xbar = runif(3) )
Error: expecting a single value
# Getting creative...
> dat %>% group_by(g) %>% function(x) x[c(1,1,1,2),]
# Nope.
我该怎么做?
我正在对抗的具体用例是分割一个 \\\
-delimited文本字段并使其长,但是我使用<$ c $
The specific use case I'm butting up against is splitting a \n
-delimited text field and making it "long," but I use this feature of ddply
all the time for many purposes.
推荐答案
尝试这样:
dat %>%
group_by( g ) %>%
do( .[c(1,1,1,2), ] ) %>%
ungroup()
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