Random sampling and removing data

Question

sooraj ajith 2021-2-3

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https://ww2.mathworks.cn/matlabcentral/answers/735112-random-sampling-and-removing-data

评论： KSSV 2021-2-3

Hi,

I have a set of data points = [10 10 0; 10 13 0; 10 16 0;20 10.1 0; 20 13.1 0 ; 20 16.1 0; 30 10.2 0;30 13.2 0; 30 16.2 0;40 10.3 0; 40 13.3 0; 40 16.3 0; 50 13.4 0];

and for every iteration, i want to select a random set of values and for next iteration previously selected set of value should be remove from the datapoints

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Answer 1

KSSV 2021-2-3

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You can make the data random by using the below and then you can pick the points.

points = [10 10 0; 10 13 0; 10 16 0;20 10.1 0; 20 13.1 0 ; 20 16.1 0; 30 10.2 0;30 13.2 0; 30 16.2 0;40 10.3 0; 40 13.3 0; 40 16.3 0; 50 13.4 0];
idx = randperm(size(points,1)) ;
%% shuffle the points 
points_random = points(idx,:) ;

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sooraj ajith 2021-2-3

Thank you. It is what i wanted

KSSV 2021-2-3

Thanks is accepting the answer.. :)

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Answer 2

Mara 2021-2-3

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https://ww2.mathworks.cn/matlabcentral/answers/735112-random-sampling-and-removing-data#answer_613902

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Hey Sooraj,

it is not all clear to me whether you want to choose entire rows/columns of your matrix or completely random sets of numbers. So I want to make this suggestion to choose rows by random indexing and deleting them thereafter.

But if KSSVs solution suffices for your purpose, it should be better as it involves less computation. You might want to initialize the variables before looping, too.

dataset       = [10 10 0; 10 13 0; 10 16 0;20 10.1 0; 20 13.1 0 ; 20 16.1 0; 30 10.2 0;30 13.2 0; 30 16.2 0;40 10.3 0; 40 13.3 0; 40 16.3 0; 50 13.4 0];
nr_picks = 3;
for i = 1:nr_picks
    random_row_index    = randi(size(dataset, 1)); % pick random row index
    extracted_row       = dataset(random_row_index, :); % extract the entire row
    dataset(random_row_index, :) = []; % delete this row from the dataset
end