Num2cell question

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I have a data of size 1440*720*102 double. I want to convert it into a cell structure, I used num2cell but I am hitting bricks !

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Answer 1

Torsten 2022-11-23

在 MATLAB Online 中打开

0 个投票

Most probably too large for your computer:

A = rand(12,3,5)
A = 
A(:,:,1) =

    0.3275    0.4565    0.9054
    0.7983    0.5975    0.2010
    0.2198    0.2999    0.8786
    0.9899    0.9124    0.3179
    0.9665    0.3451    0.1311
    0.2861    0.9911    0.9365
    0.9874    0.9247    0.4403
    0.8435    0.8488    0.3430
    0.0910    0.2928    0.0985
    0.0995    0.6732    0.3981
    0.2617    0.1184    0.3649
    0.8339    0.7366    0.2909


A(:,:,2) =

    0.0398    0.1426    0.6770
    0.9303    0.4939    0.5339
    0.0665    0.4595    0.4976
    0.0761    0.6740    0.3230
    0.3805    0.4837    0.0900
    0.8389    0.8596    0.8293
    0.9910    0.0807    0.7654
    0.4896    0.4105    0.4247
    0.6137    0.7339    0.8006
    0.4384    0.6656    0.1509
    0.2105    0.3942    0.8460
    0.5686    0.6290    0.2638


A(:,:,3) =

    0.0842    0.9096    0.2395
    0.3705    0.6611    0.8899
    0.7653    0.4083    0.4778
    0.9416    0.9301    0.0006
    0.8523    0.7219    0.8770
    0.5199    0.7490    0.7645
    0.8845    0.4652    0.6654
    0.4324    0.0940    0.9906
    0.0468    0.1547    0.0576
    0.6182    0.9954    0.8048
    0.1842    0.8711    0.4498
    0.8104    0.3860    0.5313


A(:,:,4) =

    0.4143    0.7380    0.2589
    0.4286    0.1949    0.4761
    0.2196    0.3809    0.5016
    0.3815    0.2741    0.9400
    0.2250    0.9047    0.9829
    0.9862    0.1425    0.0772
    0.5833    0.3206    0.3210
    0.0632    0.4139    0.7289
    0.5868    0.7736    0.5324
    0.3161    0.4334    0.0550
    0.7031    0.6694    0.0109
    0.5341    0.4399    0.1195


A(:,:,5) =

    0.5985    0.4265    0.0811
    0.1229    0.3392    0.7524
    0.2603    0.7418    0.4899
    0.1817    0.9131    0.3994
    0.2359    0.3633    0.3610
    0.1934    0.6980    0.0690
    0.7655    0.2662    0.3542
    0.4334    0.5158    0.1679
    0.9395    0.6295    0.1512
    0.7503    0.1131    0.1357
    0.9663    0.4720    0.1601
    0.6951    0.1670    0.1415
A = num2cell(A)
A = 12×3×5 cell array
A(:,:,1) = 

    {[0.3275]}    {[0.4565]}    {[0.9054]}
    {[0.7983]}    {[0.5975]}    {[0.2010]}
    {[0.2198]}    {[0.2999]}    {[0.8786]}
    {[0.9899]}    {[0.9124]}    {[0.3179]}
    {[0.9665]}    {[0.3451]}    {[0.1311]}
    {[0.2861]}    {[0.9911]}    {[0.9365]}
    {[0.9874]}    {[0.9247]}    {[0.4403]}
    {[0.8435]}    {[0.8488]}    {[0.3430]}
    {[0.0910]}    {[0.2928]}    {[0.0985]}
    {[0.0995]}    {[0.6732]}    {[0.3981]}
    {[0.2617]}    {[0.1184]}    {[0.3649]}
    {[0.8339]}    {[0.7366]}    {[0.2909]}


A(:,:,2) = 

    {[0.0398]}    {[0.1426]}    {[0.6770]}
    {[0.9303]}    {[0.4939]}    {[0.5339]}
    {[0.0665]}    {[0.4595]}    {[0.4976]}
    {[0.0761]}    {[0.6740]}    {[0.3230]}
    {[0.3805]}    {[0.4837]}    {[0.0900]}
    {[0.8389]}    {[0.8596]}    {[0.8293]}
    {[0.9910]}    {[0.0807]}    {[0.7654]}
    {[0.4896]}    {[0.4105]}    {[0.4247]}
    {[0.6137]}    {[0.7339]}    {[0.8006]}
    {[0.4384]}    {[0.6656]}    {[0.1509]}
    {[0.2105]}    {[0.3942]}    {[0.8460]}
    {[0.5686]}    {[0.6290]}    {[0.2638]}


A(:,:,3) = 

    {[0.0842]}    {[0.9096]}    {[    0.2395]}
    {[0.3705]}    {[0.6611]}    {[    0.8899]}
    {[0.7653]}    {[0.4083]}    {[    0.4778]}
    {[0.9416]}    {[0.9301]}    {[6.3608e-04]}
    {[0.8523]}    {[0.7219]}    {[    0.8770]}
    {[0.5199]}    {[0.7490]}    {[    0.7645]}
    {[0.8845]}    {[0.4652]}    {[    0.6654]}
    {[0.4324]}    {[0.0940]}    {[    0.9906]}
    {[0.0468]}    {[0.1547]}    {[    0.0576]}
    {[0.6182]}    {[0.9954]}    {[    0.8048]}
    {[0.1842]}    {[0.8711]}    {[    0.4498]}
    {[0.8104]}    {[0.3860]}    {[    0.5313]}


A(:,:,4) = 

    {[0.4143]}    {[0.7380]}    {[0.2589]}
    {[0.4286]}    {[0.1949]}    {[0.4761]}
    {[0.2196]}    {[0.3809]}    {[0.5016]}
    {[0.3815]}    {[0.2741]}    {[0.9400]}
    {[0.2250]}    {[0.9047]}    {[0.9829]}
    {[0.9862]}    {[0.1425]}    {[0.0772]}
    {[0.5833]}    {[0.3206]}    {[0.3210]}
    {[0.0632]}    {[0.4139]}    {[0.7289]}
    {[0.5868]}    {[0.7736]}    {[0.5324]}
    {[0.3161]}    {[0.4334]}    {[0.0550]}
    {[0.7031]}    {[0.6694]}    {[0.0109]}
    {[0.5341]}    {[0.4399]}    {[0.1195]}


A(:,:,5) = 

    {[0.5985]}    {[0.4265]}    {[0.0811]}
    {[0.1229]}    {[0.3392]}    {[0.7524]}
    {[0.2603]}    {[0.7418]}    {[0.4899]}
    {[0.1817]}    {[0.9131]}    {[0.3994]}
    {[0.2359]}    {[0.3633]}    {[0.3610]}
    {[0.1934]}    {[0.6980]}    {[0.0690]}
    {[0.7655]}    {[0.2662]}    {[0.3542]}
    {[0.4334]}    {[0.5158]}    {[0.1679]}
    {[0.9395]}    {[0.6295]}    {[0.1512]}
    {[0.7503]}    {[0.1131]}    {[0.1357]}
    {[0.9663]}    {[0.4720]}    {[0.1601]}
    {[0.6951]}    {[0.1670]}    {[0.1415]}

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John D'Errico 2022-11-23

在 MATLAB Online 中打开

To expand on what @Torsten said:

A = rand(10);
C = num2cell(A);
whos A C
  Name       Size            Bytes  Class     Attributes

  A         10x10              800  double              
  C         10x10            11200  cell                

So the cell array, contining the same data, used considerably more memory (14x), to store those same elements.

11200/800
ans = 14

You have an array of size 1440*720*102. Assuming each element is a double, that is

1440*720*102*8/(1024^3)
ans = 0.7879

So a little under 1 gigabyte of RAM, just to store that array. But, as a cell array, of individual elements, you might need as much as

1440*720*102*8/(1024^3)*14
ans = 11.0310

11 gigabytes of RAM to store that cell array, IF you convert each element into one cell.

If you are being mroe efficient, and each cell is itslef more than one element, things might not be so inefficient. But you will still need something on the order of 11 gigabytes of free memory.

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Answer 2

Image Analyst 2022-11-23

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You say "cell structure" but it's ambiguous whether you want a structure array or a cell array.

Why on earth would you want to convert it to a cell array? Cell arrays take up way more memory than numerical arrays and are slower and more inefficient. I'd just leave your data as it is.

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