sum of range of matrix elements from starting and end point

I have 90000*20 matrix i want to add 50 elements of 18th column successively. how can i do so please help.also could you please tell how to do sum of elements in the vector if the starting and end point is known.

Answer 1

[KALYAN ACHARJYA]

Lets say the matrix data is variable name as "mat"

result=sum(mat(1:50,18))

"could you please tell how to do sum of elements in the vector if the starting and end point is known".

If 1-D vector, you can use sum directly

result=sum(mat(Start_index:End_index))

For 2 D case

data=mat(From rows:Till Rows number,From columns:Till Columns number)
result=sum(data(:))

[Abhijit Sardar]

how to calculate the sum of consecutive 50 elements throught out for the entire elements in that coulmn.

[KALYAN ACHARJYA]

sum(data(1:50:column_num))
%.........^ change the row indices as per requirement

[Abhijit Sardar]

No, i meant first i want sum of 1 - 50 elements and then 2-51,3-52 like so on... i am coding like this but in 'res' i am only getting one answer. i want the consecutive sum of 50 elements correspoing to all 90000 row elements.

for i = 1:p-50

res = sum(m(i:i+50,18))

end

[KALYAN ACHARJYA]

In that case you have to use array indexing

l=1;
res=zeros(1,,,,expected_num_of interation); % Must do
for i = 1:p-50
 res(l)= sum(m(i:i+50,18))
end

In this case you can avoid loop, please use movsum, as follows (Recommended)

data=m(:,18);
sum_result=movsum(data,50)