# for loop starting from 1

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Morten Jørgensen on 11 Apr 2019
Edited: Bob Thompson on 11 Apr 2019
Hi
Is there a way to make this start from 1, when 1 is not in Player{4,1}(:,1)?
i want to take the sum from 1:127, 127:162, 162:285 and so on, is this possible?
thanks
% Player{2,1}(:,2) is a vector with a length of 590
% Player{4,1}(:,1) =
127
162
285
300
316
323
493
500
584
for j = 1:length(Player{4,1})-1
Output(j,1) = sum(Player{2,1}(Player{4,1}(j,1):Player{4,1}(j+1,1),2))
end
##### 3 CommentsShow 1 older commentHide 1 older comment
Morten Jørgensen on 11 Apr 2019
thanks.
the first number of a is 127, but i want to make it start from1 instead of 127.
would it be easier to just alter the vector a to:
1
127
162
285
300
316
323
493
500
584
so i get the sum of b 1:127 in the first ?
Bob Thompson on 11 Apr 2019
Yes, it would be easier to make that modification. Because you are only looking to use 1 initially, it would be possible to add that as a boundary with an if statement, but that is making things much more complicated than simply changing 'a'.

Jan on 11 Apr 2019
a = Player{4,1}(:, 1);
b = Player{2,1}(:, 2);
Output = zeros(length(a)-1, 1); % Pre-allocate
Output(1) = sum(b(1:a(j+1)));
for j = 2:length(a)-1
Output(j) = sum(b(a(j):a(j+1)));
end
Or
Output = zeros(length(a)-1, 1); % Pre-allocate
a(1) = 1;
for j = 1:length(a)-1
Output(j) = sum(b(a(j):a(j+1)));
end
Bob Thompson on 11 Apr 2019
Edited: Bob Thompson on 11 Apr 2019
Wouldn't using a(1) = 1; remove the current value of a(1) = 127? I would think that this would mean that Output(1) would end up spanning from 1:162, instead of 1:127. I would think you would need to concat instead.
a = Player{4,1}(:, 1);
a = [1; a];

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