for loop starting from 1

Question

Morten Jørgensen 2019-4-11

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https://ww2.mathworks.cn/matlabcentral/answers/455750-for-loop-starting-from-1

编辑： Bob Thompson 2019-4-11

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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

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Morten Jørgensen 2019-4-11

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 2019-4-11

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'.

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Answer 1

Jan 2019-4-11

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/455750-for-loop-starting-from-1#answer_370190

在 MATLAB Online 中打开

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

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Bob Thompson 2019-4-11

编辑：Bob Thompson 2019-4-11

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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for loop starting from 1

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