[R] Help/ Mathematics

[Ahmed Attia]

Hi R users,

I need your help to write a code in r that does the following
calculation from three different datasets;

ac = 1/sum (NPP from date 1 to date 2, dataset=1) * (biomass at date 2
-biomass at date 1, dataset = 2) + (littfall at date 2, dataset=3).

all the dates are in yr-month-day format. Which library or function
Should I use to tell R do these calculations of these variables at
different dates.

I appreciate your help.

Ahmed Attia, Ph.D.
Agronomist & Soil Scientist