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stepwise mean value of array

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Rica
Rica 2012-11-14
Hi!
% a= [1 2 5 6 4 7......]
how to get the mean value :
mean_a =[mean(a(1),a(110)),mean(a(2),a(120)), mean(a(3),a(130))............]
thanky
  2 个评论
Image Analyst
Image Analyst 2012-11-14
What do you mean by mean(a(1),a(110))? Is that the mean of all elements from 1 to 110, like this: mean(a(1:110))?
Rica
Rica 2012-11-14
Hi!
that means:the mean value of element 1 and element 100, nad the mean value of element 2 and element 200 an so on ..... thanks

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采纳的回答

Jan
Jan 2012-11-14
x = rand(1, 1000);
index1 = 1:10;
index2 = 100:100:1000;
result = (x(index1) + x(index2)) * 0.5;

更多回答（3 个）

Dian Permatasari
Dian Permatasari 2012-11-14
if the calculation of some matrix, you can use:
B=mean([A(1) A(2) A(3) ...])
Walter Roberson
Walter Roberson 2012-11-14
N = 7; %or as appropriate
LB = 1 : N; %the lower bounds for the means
UB = (1:N)*100; %or as appropriate for the upper bound
S = cumsum(a); %the trick!
mean_a = (S(UB) - S(LB)) ./ (UB - LB + 1);
Andrei Bobrov
Andrei Bobrov 2012-11-14
编辑：Andrei Bobrov 2012-11-14
"...the mean value of element 1 and element 100, and the mean value of element 2 and element 200 an so on..." :
k = 100:100:numel(a);
mean_a = mean(a([(1:numel(k))', k']),2);

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