How to find the maximum value for each 24 rows in an array?

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BN 2019-11-4

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回答： BN 2019-11-14

采纳的回答： Shubham Gupta

myarrays.mat

Hello,

I have a 3d array, precip= :,:, 8760. in fact 8760 rows are available in one column. I want to find the maximum value in this column 24-by-24 in rows. And saving the bigger value and eliminate the smaller one. and do it for all 8760-row

so if the dimension before doing this is precip = :, :, 8760, after this work should be precip = :, :, 365.

I wanna practical this for a 3d array which the third dimension is what I talking about.

I'm attaching all my array. as the volume of original file is so big I cut first 72 rows and attach it

Thank you

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Shubham Gupta 2019-11-13

编辑：Shubham Gupta 2019-11-13

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Let's take a example with an array of dimension 2x3x4. So time = 1hr, 2hr, 3hr & 4hr. At each hour let's assume random data for temp & assume that on this earth 1 day is of 2hr.

t = 1hr
T = [20 30 40
     50 60 70];
 
t = 2hr 
T = [30 50 70
    80 90 75];
t = 3hr 
T = [-20 40 10
    15 900 80];
t = 4hr
T = [25 55 11
    10 -45 9];

What is the output that you are expecting in this hypothetical situation? I understand your 3rd dimesion (pages) will be 2 but I still don't know what do you want to do with the 1st & 2nd dimesion. I am expecting your output to be:

Day = 1
T = ??
Day = 2
T = ??

BN 2019-11-13

在 MATLAB Online 中打开

ok if assume that on this earth 1 day is of 2hr, then the output is:

Day = 1
T = 90
Day = 2
T = 900

I don't want to change the first and second dimensions.

input = :, :, 87600

output = :, :, 365 or 366

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采纳的回答

Shubham Gupta 2019-11-14

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https://ww2.mathworks.cn/matlabcentral/answers/489065-how-to-find-the-maximum-value-for-each-24-rows-in-an-array#answer_401420

编辑：Shubham Gupta 2019-11-14

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According to the comments, you have provided, this will produce the desired output :

yd = max(max(mn2t)); % first find maximum for each hour
y = reshape(yd,24,1,size(yd,3)/24); % reshape it by day
output = max(y); % find maximum of each day

Let me know if this works !

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BN 2019-11-14

Dear Shubham,

It's works perfect for the array. thank you so much. I gonna accept your answer but webpage says: An Error Occurred (Unable to complete the action because of changes made to the page. Reload the page to see its updated state)

I have faced this error previously, and I know a few hours later it will be fixed and I can click on accept answer.

but now just in a case do you know how to use this code when mn2t is cell (34*1 cell) (instead of an array) and using this code for all 34 rows of this cell (the cell consists of 34 of this 3d array?

Thank you - I will accept your answer.

Shubham Gupta 2019-11-14

在 MATLAB Online 中打开

Simply use for loop mn2t:

output = cell(size(mn2t));
for i = 1:length(mn2t)
    mn2t_mat = mn2t{i}; % extract matrix of ith element
    yd = max(max(mn2t_mat)); % first find maximum for each hour
    y = reshape(yd,24,1,size(yd,3)/24); % reshape it by day
    output{i} = max(y); % find maximum of each day
end