Mean neighbour values of a vector

Question

wenyi xiao 2020-11-18

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/652238-mean-neighbour-values-of-a-vector

回答： Srivardhan Gadila 2020-11-24

采纳的回答： Srivardhan Gadila

Hi,

I got an original data(a vector, size is 1*N):

the format is like this: 𝑠1:𝑥1,𝑥2,𝑥3…𝑥𝑁

And I need 20 series,

The scale 2 series was obtained by averaging two successive values from the original series. Scale 3 was obtained by averaging every three original values and so on as shown in equation.

𝑠2:(𝑥1+𝑥2)/2,(𝑥3+𝑥4)/2,…,(𝑥𝑁−1+𝑥𝑁)/2

𝑠20:(𝑥1+⋯+𝑥20)/20,…,(𝑥𝑁−20+⋯+𝑥𝑁)/20

How can I achieve this in Matlab?

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Ameer Hamza 2020-11-18

Suppose you have an odd number of elements? How to calculate s2 in that case? For example, x have 5 elements.

s2 =: (x1+x2)/2, (x3+x4)/2, x5+????

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Answer 1

Srivardhan Gadila 2020-11-24

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/652238-mean-neighbour-values-of-a-vector#answer_554958

在 MATLAB Online 中打开

You can learn the essentials of MATLAB throught the MATLAB Onramp course. If you are already familiar then you can refer to the documentation of for, mean & Loops and Conditional Statements.

For the above cases listed 𝑠2:(𝑥1+𝑥2)/2,(𝑥3+𝑥4)/2,…,(𝑥𝑁−1+𝑥𝑁)/2 and 𝑠20:(𝑥1+⋯+𝑥20)/20,…,(𝑥𝑁−20+⋯+𝑥𝑁)/20, you can do something like below using arrayfun:

s1 = randn(40,1);
N = numel(s1);
m = 2;
s2 = arrayfun(@(i)mean(s1(m*(i-1)+1:m*i)),1:floor(N/m))
m = 20;
s20 = arrayfun(@(i)mean(s1(m*(i-1)+1:m*i)),1:floor(N/m))

Note that as Ameer Hamza rightly mentioned, you will have to figure out the code in the case where N is not exactly divisible by m.