arrayDatastore Read cut dimension

Question

Odo Luo 2022-4-18

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1699025-arraydatastore-read-cut-dimension

评论： Walter Roberson 2022-4-18

For a segmentation task I have a Hx Wx M items as matrix, I gonna convert into a logical array.

I would like to read these items into an arrayDatastore and tried following (simplified code):

for counter = 1:20
    A= magic(10);
    resultItem= cat(3,A,A,A);
    result(counter,:,:,:)=resultItem;
end
result=logical(result<5& result>2);
ds=arrayDatastore(result,"ReadSize",1,"OutputType","same");

The read funktion sadly delivers a 1x4 dimensional array instead of 1x3. How can I clipp the first dimension - the counter - away ?

Or any other solution how to read everything into an arrayDatastore during a loop?

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Answer 1

Walter Roberson 2022-4-18

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1699025-arraydatastore-read-cut-dimension#answer_945035

在 MATLAB Online 中打开

result(:,:,:,counter)=resultItem;

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Odo Luo 2022-4-18

Sorry, I do not understand your answer

This still leaves me with a 1x4 array, just with the counter at the end

Walter Roberson 2022-4-18

在 MATLAB Online 中打开

Sorry, it does not appear to be possible. The closest appears to be that you can return a scalar cell that is 3 dimensions. If you need a numeric return instead of a scalar cell then you are going to get a 4 dimensional object that you would then have to reshape() or permute() or squeeze()

for counter = 1:20
    A = magic(10);
    resultItem = cat(3,A,A,A);
    result(:,:,:,counter) = resultItem;
end
result = logical(result<5& result>2);
ds = arrayDatastore(result,"ReadSize", 1, "OutputType", "cell", "IterationDimension", 4);
test1 = read(ds);
test2 = read(ds);
whos
  Name             Size                 Bytes  Class                                 Attributes

  A               10x10                   800  double                                          
  cmdout           1x33                    66  char                                            
  counter          1x1                      8  double                                          
  ds               1x1                      8  matlab.io.datastore.ArrayDatastore              
  result          10x10x3x20             6000  logical                                         
  resultItem      10x10x3                2400  double                                          
  test1            1x1                    404  cell                                            
  test2            1x1                    404  cell                                            
size(test1{1})
ans = 1×3
    10    10     3