selection of data from matrix

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MUKESH KUMAR
MUKESH KUMAR el 17 de Nov. de 2017
Editada: MUKESH KUMAR el 18 de Nov. de 2017
I have a dataset lets say a matrix of 100 rows and 5 columns, each row represents a dataset.Now I want to select 5 any rows(datasets) initially, then further I want to select 4 rows(dataset) except initially 5 rows should not be repeated, then next I want to select 10 rows except for initially selected rows (those 9 rows should not be repeated here) in before and so on..... one thing to remember that one rows should be selected once here.

Respuesta aceptada

Andrei Bobrov
Andrei Bobrov el 17 de Nov. de 2017
data = randi([-41 78],100,5);
ii = randperm(size(data,1));
k = [5 4 10];
out = mat2cell(data(ii(1:sum(k)),:),k,size(data,2));
  1 comentario
MUKESH KUMAR
MUKESH KUMAR el 18 de Nov. de 2017
Editada: MUKESH KUMAR el 18 de Nov. de 2017
short and sweet answer, thanks

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Más respuestas (3)

KL
KL el 17 de Nov. de 2017
Editada: KL el 18 de Nov. de 2017
One easy alternative is to shuffle the row of your matrix first and then extract them from top to bottom,
data = [(1:100).' rand(100,5)]; %dummy data
indx = randperm(size(data,1));
data = data(indx,:);
numberofRowsWanted = 4;
data_ext = data(1:numberofRowsWanted,:);
Another alternative is to split and put them all in a cell array.
data = [(1:100).' rand(100,5)]; %dummy data
indx = randperm(size(data,1)); %generate random indices without repeating
splits = [4,5,10]; %how many rows you want to extraxt each time, extend it as you wish
%now, use arrayfun to extract those rows and store them in a cell array.
data_ext = arrayfun(@(x,y) data(indx(x:y),:),[1 splits+1],[splits(1) splits(1:end-1)+splits(2:end)],'uni',0);

KSSV
KSSV el 17 de Nov. de 2017
Check the below example code:
K = 1:100 ;
pick = [5 4 9 10] ;
for i = 1:length(pick)
take = randsample(K,pick(i))
% remove the selected numbers
K = setdiff(K,take) ;
end
  2 comentarios
MUKESH KUMAR
MUKESH KUMAR el 17 de Nov. de 2017
if the size of K matrix like 100*5 then this code doesn't work.any further solution for it , Thanks
KL
KL el 18 de Nov. de 2017
It indeed works, in fact all of the solutions here do what you want, they are just examples. Instead of just copy-pasting, try and understand how it works.

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Guillaume
Guillaume el 17 de Nov. de 2017
There are many ways you could do this. You could keep track of the row you've selected and exclude them from the set of rows to select from, but probably the simplest way would be to remove the rows you've selected from your dataset.
dataset = rand(100, 5); %demo dataset
while ~isempty(dataset)
%select 5 rows at random:
numrowstoselect = 5; %adjust as required
selectedrows = randperm(size(dataset, 1), min(numrowstoselect, size(dataset, 1));
selecteddataset = dataset(selectedrows, :);
%remove selected rows from dataset so they can't be selected again
dataset(selectedrows, :) = [];
end

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