I have two vectors. The first one contains values representing the annual energy demand. It has a length of 22 which represents 22 years. The second one is much larger and contains energy yield values in descending order.

Here is some code for reproduction:

# create demand vector
demand.vec <- c(427839, 408392, 388944, 369497.652793, 350050, 330603, 311155, 291708, 272261, 252814, 233366, 213919, 
                194472, 175025, 155577, 136130, 116683, 97236,  77788,  58341,  38894, 19447)

# create yield vector
set.seed(10)
yield.vec <- sort(runif(n = 10500, min = 800, max = 950), decreasing= T)

The goal is now for each year to sum up as many values as needed from yield.vec to reach at least the energy demand for the respective year. This means that for the first year, so many values from yield.vec should be summed up that 427839 is reached. In the second year from the remaining values of yield.vec the values should be summed up so that 408392 is reached and so forth.

As output I would need a vector with the resulting achieved annual energy yields and ideally also a vector that shows which values of the yield.vec were used for the respective years. So for the first year the value would be 428011.69755 since it is the result of sum(yield.vec[1:452]) and larger than demand.vec[1]. In this case the first value of the second output vector would be 452 since as many values were needed.

Any body with an idea?