data frame of dimensions 24 by 8.
Example for a given day of the year to illustrate the
CanA function.
LAI: leaf area index.
year: year.
doy: 124 in this case.
hour: hour of the day, (0--23).
solarR: direct solar radiation.
DailyTemp.C: hourly air temperature (Celsius).
RH: relative humidity, (0--1).
WindSpeed: 4.1 m s^{-1} average daily value in this
case.