列中的每次更改增加 1 [英] Increment by 1 for every change in column

问题描述

假设我有以下数据框

set.seed(123)
df <- data.frame(var1=(runif(10)>0.5)*1)

var1 可以有任何类型/数量的级别，而不是 0 和 1s

var1 could have any type / number of levels not specifically 0 and 1s

我想创建一个 var2 每次 var1 使用 for 循环 改变而增加 1>

I would like to create a var2 which increments by 1 every time var1 changes without using a for loop

这种情况下的预期结果是:

Expected result in this case is:

data.frame(var1=(runif(10)>0.5)*1, var2=c(1, 2, 3, 4, 4, 5, 6, 6, 6, 7))

var1 var2
   0    1
   1    2
   0    3
   1    4
   1    4
   0    5
   1    6
   1    6
   1    6
   0    7

数据框的另一个选项可能是:

Another option for the data frame could be:

df <- data.frame(var1=c("a", "a", "1", "0", "b", "b", "b", "c", "1", "1"))

在这种情况下，结果应该是:

in this case the result should be:

var1 var2
   a    1
   a    1
   1    2
   0    3
   b    4
   b    4
   b    4
   c    5
   1    6
   1    6

推荐答案

以弗利克先生的回答为基础:

Building on Mr Flick answer:

df$var2 <- cumsum(c(0,as.numeric(diff(df$var1))!=0))

但是如果你不想使用 diff 你仍然可以使用:

But if you don't want to use diff you can still use:

df$var2 <- c(0,cumsum(as.numeric(with(df,var1[1:(length(var1)-1)] != var1[2:length(var1)]))))

它从 0 开始，而不是从 1 开始，但我相信如果您愿意，您会知道如何更改它.

It starts at 0, not at 1 but I'm sure you see how to change it if you want to.

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