Appending columns using cbind
# Random day, month and year predictors, indicating time of CO2 measurements
day <- sample(c(1:30), nrow(CO2), TRUE)
month <- sample(c(1:12), nrow(CO2), TRUE)
year <- sample(c(2013, 2014, 2015), nrow(CO2), TRUE)
CO2_time <- cbind(CO2, day, month, year) # binding the time predictors to CO2
head(CO2_time)
## Plant Type Treatment conc uptake day month year
## 1 Qn1 Quebec nonchilled 95 16.0 16 8 2014
## 2 Qn1 Quebec nonchilled 175 30.4 21 12 2014
## 3 Qn1 Quebec nonchilled 250 34.8 1 1 2013
## 4 Qn1 Quebec nonchilled 350 37.2 29 2 2014
## 5 Qn1 Quebec nonchilled 500 35.3 18 3 2014
## 6 Qn1 Quebec nonchilled 675 39.2 25 12 2014