Accessing multiple columns in cell array

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Lasse Jakobsen
Lasse Jakobsen 2021-6-9
回答： Stephen23 2021-6-9
Hi,
I need to calculate the mean of 5 measurements. The 5 measurements are presented in a 5*1 cell array. The variable is called Data.
Thus, I need the mean of:
Data{1, 1}(:,end)
Data{2, 1}(:,end)
Data{3, 1}(:,end)
Data{4, 1}(:,end)
Data{5, 1}(:,end)
How do I acces all 5 columns at once?
Thanks in advance.
-Lasse

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回答（3 个）

KSSV
KSSV 2021-6-9
编辑：KSSV 2021-6-9
A = cat(3,Data{:}) ; % convert cell array to 3D matrix
m = cell2mat(mean(A(:,end,:))) % mean of last column
Scott MacKenzie
Scott MacKenzie 2021-6-9
编辑：Scott MacKenzie 2021-6-9
You need to retrieve the elements in their underlying data type (hence the use of braces) and concatenate the values using brackets:
mean([Data{:,1}])
If indeed thare are only 5 values (measurements), then you don't need ",1". Just use
mean([Data{:}])
Have a look here for a summary of the ways to access data in a cell array. Good luck.
Stephen23
Stephen23 2021-6-9
Ran in:
Fake data:
Data = arrayfun(@(n)randi(9,2,3),1:5,'uni',0).'; % fake data
Data{:}
ans = 2×3
2 5 6 6 5 4
ans = 2×3
9 3 5 1 3 5
ans = 2×3
3 1 9 8 5 2
ans = 2×3
5 6 6 2 4 1
ans = 2×3
2 7 2 1 7 5
Method one:
M = mean(cat(3,Data{:}),3);
M = M(:,end)
M = 2×1
5.6000 3.4000
Method two:
M = mean(cell2mat(reshape(Data,1,1,[])),3);
M = M(:,end)
M = 2×1
5.6000 3.4000
Method three:
M = mean(cell2mat(cellfun(@(m)m(:,end),Data.','uni',0)),2)
M = 2×1
5.6000 3.4000
Method four:
M = mean(cell2mat(arrayfun(@(n)Data{n}(:,end),1:numel(Data),'uni',0)),2)
M = 2×1
5.6000 3.4000

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