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Increase by 1 for each column change in R
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Increase by 1 for each column change in R
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Lets say I have the following data frame
set.seed(123)
df <- data.frame(var1=(runif(10)>0.5)*1)
var1 could have any type / number of levels not specifically 0 and 1s
I would like to create a var2 which increments by 1 every time var1 changes without using a for loop
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
Another option for the data frame could be:
df <- data.frame(var1=c("a", "a", "1", "0", "b", "b", "b", "c", "1", "1"))
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
Building on Mr Flick answer:
df$var2 <- cumsum(c(0,as.numeric(diff(df$var1))!=0))
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)]))))
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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