Concatenate elements of tall array (big data)

Question

Collin Tuttle 2017-6-20

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https://ww2.mathworks.cn/matlabcentral/answers/345588-concatenate-elements-of-tall-array-big-data

评论： Collin Tuttle 2017-6-23

Hello,

I am new to working with big data and cannot figure out how to do much.

I created a datastore and subsequent tall array from 35 files, each file has one variable in the form of a 320x104x14597 matrix.

It appears that the tall array keeps each as a separate entry. How would I go about either concatenating them (into a 320x104x14597x35 matrix), or taking a mean across the 35 files? (I'm apparently using the mean and cat commands incorrectly with the tall array).

Thanks!

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Answer 1

Gopeshh Raaj 2017-6-23

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编辑：Gopeshh Raaj 2017-6-23

在 MATLAB Online 中打开

I understand that you want to concatenate all the 35 3-D matrices to a 4-D matrix and also want to take the mean across the data from all the 35 files.

The solution to this is to use "cat" function and the "mean" function. Example code snippet on how to use "cat" and "mean" for your situation is shown below.

 a = ones(320,104,1457);
 b = ones(320,104,1457);
 c = cat(4,a,b);
 d = mean(c,4);

So, like this you can concatenate all the 35 files which you have by using a loop.

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Collin Tuttle 2017-6-23

The thing is that the data is very large and I cannot work with the data this way because it exceeds memory allowance. I am trying to do this within a tall array.

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