The Orange data frame from the datasets package has $35$ rows and $3$ columns of records of the growth of orange trees.

Tree $-$ an ordered factor indicating the tree on which the measurement is made. The ordering is according to increasing maximum diameter.

age $-$ a numeric vector giving the age of the tree $($days since $1968/12/31)$

circumference $-$ a numeric vector of trunk circumferences $($mm$).$ This is probably $$circumference at breast height$,$ a standard measurement in forestry.

Using head$($Orange$),$ we show the first couple of observations and plot cricumference vs$.$ age in the following cell: