# Let's keep working with our CO2copy data frame 

## Subsetting by variable name 
CO2copy[,c("Plante", "absortionRel")] # Selects only "Plante" and "absortionRel" columns. (Don't forget the ","!)

## Subsetting by row 
CO2copy[1:50,] # Subset data frame from rows from 1 to 50 

### Subsetting by matching with a factor level 
CO2copy[CO2copy$Traitement == "nonchilled",] # Select observations matching only the nonchilled Traitement. 

### Subsetting according to a numeric condition 
CO2copy[CO2copy$absortion >= 20, ] # Select observations with absortion higher or equal to 20  

### Conditions can be complimentary -The & (and) argument-
CO2copy[CO2copy$Traitement  == "nonchilled" & CO2copy$absortion >= 20, ]

# We are done playing with the dataset copy. Let's erase it.
CO2copy <- NULL