R总FUN =头 [英] R Aggregate FUN=head

问题描述

我想通过两列（顺序和程序）聚合一个表（选项卡），以获取采样大小的第一行（FUN = head）。

I would like to aggregate a table (tab) by two columns (sequence and program) to get the top row of samplesize (FUN=head).

sq <- c(1,1,1,1,1,1) 
prog<- c('A','A','B','B','C','C') 
ss <- c(47,47,28,28,47,47) 
tab<- data.frame(sq,prog,ss)

总体给了我一个奇怪的结果

Aggregate is giving me an odd result in that if the sample size is the same for a DIFFERENT combination of sequence and program- it omits it.

agg  <- aggregate(cbind(sq,prog) ~ ss, data = tab, FUN=head,1,na.rm=TRUE)

我很困惑为什么发生这种情况，以及为什么当它是文本（A，B，C）时它将程序更改为数字序列。

I'm confused why this is occurring and why it is changing the program to a numerical sequence when it is text (A,B,C).

推荐答案

这是因为默认情况下， data.frame 会从字符列。您需要：

It's because by default, data.frame creates a factor from character columns. You need:

tab <- data.frame(sq, prog, ss, stringsAsFactors = FALSE)

编辑：我个人认为 dplyr 软件包非常直观。为了您的结果，我将使用：

I personally find the dplyr package very intuitive. For your result, I'd use:

library(dplyr)
tab %>%
  group_by(sq, prog) %>% 
  filter(row_number() == 1)

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