Find highest third of values in dateset?

Question

Peter Mills 2018-1-12

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/376897-find-highest-third-of-values-in-dateset

编辑： Star Strider 2018-1-12

采纳的回答： Star Strider

在 MATLAB Online 中打开

WaveHeight=[3 1 5 2 3.1 6 5.5 3 2.5];

We need to find the highest 1/3:

HighestThird=[6 5.5 5]

But what if we what a function that will calculate the mean of the heights 1/3 of WaveHeight with the length of WaveHeight being a variable which may be large?

Please see my comment in this linked post How to determine significant wave height from time series data in Matlab

E.g.

WaveHeight=randi(1000,1,1000);
HighestThird=

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Adam 2018-1-12

编辑：Adam 2018-1-12

"calculate the mean of the heights 1/3 of WaveHeight"

I don't understand what this means. What is it you want to take the mean of and what is it you want 1/3 of?

Since you are starting your own question here it makes sense to include your information here rather than reference a comment in another question with more information than this one. There is no guarantee that independent question (or the answer to which you replied) will not get deleted.

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Answer 1

Star Strider 2018-1-12

1
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/376897-find-highest-third-of-values-in-dateset#answer_299890

编辑：Star Strider 2018-1-12

在 MATLAB Online 中打开

One approach is to use the sort function:

WaveHeight=[3 1 5 2 3.1 6 5.5 3 2.5];
[Waves,Idx] = sort(WaveHeight, 'descend');
HighestThird = WaveHeight(Idx(1:fix(numel(Idx)/3)))
HighestThird =
            6          5.5            5

also:

HighestThird = Waves(1:fix(numel(Idx)/3))

with the same result.