Using loop to sum value of an array and summation

2 次查看（过去 30 天）
DoinK
DoinK 2023-6-10
编辑： Stephen23 2023-6-11
Ran in:
I have 2000 row vector which each array has 1008 column.
I need to sum every array to only 4 column, so every 252 item, i sum it, so the array now has 4 column.
For example, i use only 1 row vector which has 12 column and every 3 item i sum it:
J=[1 2 3 4 5 6 1 2 3 4 5 6];
for i=1:length(J)
a=sum(J(1:3));
b=sum(J(4:6));
c=sum(J(7:9));
d=sum(J(10:12));
end
p0=[a b c d]
p0 = 1×4
6 15 6 15
After that, i have to do summation:
for j=1:4
f=j*p0(j);
h(j)= sum(f);
end
h
h = 1×4
6 30 18 60
I can call 'h' too like h(3) is 18.
I can do it for small input like this, how to code for big vector?
How to summation up to 2000 vector and can call every 'h'?
May i know, summation mostly start with 0, but looping with (for) command cannot do it, ''Array indices must be positive integers or logical values."
Is there any command to use to start with 0?
  2 个评论
Stephen23
Stephen23 2023-6-10
编辑：Stephen23 2023-6-11
Ran in:
The standard MATLAB approach:
J = [1,2,3,4,5,6,1,2,3,4,5,6];
P = sum(reshape(J,[],4),1)
P = 1×4
6 15 6 15
H = J(1:4).*P
H = 1×4
6 30 18 60
DoinK
DoinK 2023-6-10
thank you sir, the code is so simple and exactly what i need.

请先登录，再进行评论。

请先登录，再回答此问题。

采纳的回答

Alan Stevens
Alan Stevens 2023-6-10
Ran in:
Here's one way:
J=[1 2 3 4 5 6 1 2 3 4 5 6];
step = 3;
ix = 1:step:numel(J);
for i = 1:numel(ix)
p(i) = sum(J(ix(i):ix(i)+step-1));
end
disp(p)
6 15 6 15

更多回答（0 个）

类别

在 Help Center 和 File Exchange 中查找有关 Creating and Concatenating Matrices 的更多信息

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by