CODEWITHSUNDEEP
rdplyr
Matt_4
Matt_4

Reputation: 157

Paste with condition and by group in R

I have a dataframe including sample names, measurement modes and starting times of measurement. The measurements are continuous and each sample is sequentially measured using all the modes.

##example
df <- data.frame(sample= rep(c(1:10),each = 4,length.out=100),
                 mode =rep_len(c("A","B","C","D"),length.out = 100),
                 time= seq(strptime("2018-1-1 0:0:0","%Y-%m-%d %H:%M:%S"),by= dseconds(200),length.out=100))

For each sample I need to get an ID composed by the sample name and the starting time of mode "B". I grouped it by sample using:

group <- function(x) cumsum(c(1, diff(x) != 0))
df$group <- group(df$sample)

then I tried to fill the new column ID using

library(dplyr)
df %>%
  group_by(group) %>%
  mutate(ID = paste(df$sample,
                    as.character(substr(df$time, start = 12,stop=16)),sep="_"))

however this code doesn't work and in addition it would paste all the starting times and not the ones corrisponding to the mode "B".

Upvotes: 1

Views: 534

Answers (1)

Bryan Adams
Bryan Adams

Reputation: 174

In your mutate command you do not need to reference your dataframe (df). You only need to reference the column ID. I believe this code will work for you.

 df%>%
  group_by(group)%>%
  mutate(ID = paste(sample,as.character(substr(time, start = 12,stop=16)),sep="_"))

Upvotes: 1

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