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Identifying where value changes in R data.frame column

Tags:

dataframe

r

I have a data.frame in R where the value column contains data of the class character. I want to identify the row numbers where value changes. In the example below I want to get out 4, 7, and 9. Is there a way to do this without looping?

df <- data.frame(ind=1:10,
 value=as.character(c(100,100,100,200,200,200,300,300,400,400)), 
 stringsAsFactors=F)
df
   ind value
1    1   100
2    2   100
3    3   100
4    4   200
5    5   200
6    6   200
7    7   300
8    8   300
9    9   400
10  10   400
like image 804
Gaurav Bansal Avatar asked Jul 17 '17 22:07

Gaurav Bansal


1 Answers

A simple solution is to use the lag function in dplyr:

which(df$value != dplyr::lag(df$value))
like image 181
thc Avatar answered Sep 20 '22 10:09

thc