Time    Concentration
12:31   128000
12:33   120500
12:34   105000
12:35   100000
12:37   115000
12:38   120000



setwd('C:\Users\.....’)
cp = read.csv(‘……...csv',header = T)
head(cp)

cp$Time = as.POSIXct(cp$Time, format = "%H:%M:%S", tz = “America/New_York”)

cp.zoo = zoo(cp[,-1], as.POSIXlt(cp[,1], format = "%H:%M:%S"))
frame.zoo = zoo(NA,seq(start(cp.zoo), end(cp.zoo), by = "min"))
df = data.frame(Time = as.POSIXlt(index(frame.zoo), format = "%H:%M:%S"))
merging = merge(df, cp, all = TRUE)