Question

Hi I have the 3 dimensional matrix in the code below. I am trying to sum all the 24 elements of “n” for every “number_panels” and “number_turbines” combination.

what I have below doesn’t sum across the 3rd dimension

for number_panels = 0:5

for number_turbines = 0:2

    for n = 1:24 % number of hours per day



hourly_deficit(number_panels + 1, number_turbines + 1, n) = Demand(n) -...     
(PV_supply(n)*number_panels) - (WT_supply(n)*number_turbines);

if hourly_deficit(number_panels + 1, number_turbines + 1, n)< 0

            hourly_deficit(number_panels + 1, number_turbines + 1, n) = 0;

        end
daily_deficit(number_panels + 1, number_turbines + 1) = sum(sum(sum(hourly_deficit(:,:,:)))) 



        hourly_total_RES(number_panels + 1, number_turbines + 1, n) = PV_supply(n)*number_panels + WT_supply(n)*number_turbines;


        if hourly_total_RES(number_panels + 1, number_turbines + 1, n) < Demand(n),

            renewables_penetration(number_panels + 1, number_turbines + 1, n) = (hourly_total_RES(number_panels + 1, number_turbines + 1, n)) / Demand(n); % ratio of renewable energy supply to demand

        else
            renewables_penetration(number_panels + 1, number_turbines + 1, n) = 1 ;

        end
             peak_deficit(number_panels + 1, number_turbines + 1,n) = max(hourly_deficit(number_panels + 1, number_turbines + 1,n));
    end

Answer 1

In MATLAB sum(X) adds all elements of matrix X in one dimension.
If you want to just calculate the sum for one specific dimension use:

 S1=sum(X,dimension);

where “dimension” is 1, or 2, or 3 for a 3D matrix.

If you want to compute over two dimensions then you can do:

 S2=sum(S1,dimension);

where dimension here is 1, or 2.

Based on your code I think this is what you should do if you want to do it in for loops:

for number_panels = 0:5
   for number_turbines = 0:2
      for n = 1:24 % number of hours per day
         hourly_deficit(number_panels + 1, number_turbines + 1, n) =...
           Demand(n) - (PV_supply(n)*number_panels) - (WT_supply(n)*number_turbines);

         if hourly_deficit(number_panels + 1, number_turbines + 1, n)< 0
           hourly_deficit(number_panels + 1, number_turbines + 1, n) = 0;
      end
      daily_deficit(number_panels + 1, number_turbines + 1) = ...
        sum(hourly_deficit(number_panels + 1, number_turbines + 1,:));
    end
 end

Look at the “:” that I added to:
sum(hourly_deficit(number_panels + 1, number_turbines + 1,:));