fast delete of rows in a table
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Francesco Giuseppe Fornari
2020년 5월 27일
댓글: Francesco Giuseppe Fornari
2020년 5월 27일
hi
I've got a table with 120k rows, and I need to delete some rows if there is a specific condition.
I wrote this:
for i=1:(size(db,1)-1)
if db.INTERVENTION(i)==1 && isequal(db.SETTLEMENTDATE(i-1),db.SETTLEMENTDATE(i)) && isequal(db.DUID(i-1),db.DUID(i))
db(i-1,:)=[];
end
end
This code takes a long time to execute.
Is there a faster way?
thanks!
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채택된 답변
Image Analyst
2020년 5월 27일
Try this:
numRows = size(db,1)-1;
rowsToDelete = false(numRows, 1);
for k = 2 : numRows % Has to start at 2, right? Since you're using k-1. Don't use i, the imaginary variable, as a loop index.
if db.INTERVENTION(k)==1 && isequal(db.SETTLEMENTDATE(k-1),db.SETTLEMENTDATE(k)) && isequal(db.DUID(k-1),db.DUID(k))
rowsToDelete(k) = true;
end
end
db(rowsToDelete, :) = []; % Remove these rows.
% Or equivalently
%db = db(~rowsToDelete, :); % Extract everything BUT the rows to delete.
댓글 수: 3
Image Analyst
2020년 5월 27일
I think the reason being is that when you removed a single row from the table, it had to rebuild the table each time. If you give it a vector, it has to rebuild the table only once.
추가 답변 (1개)
darova
2020년 5월 27일
Write indices and delete outside the for loop
ind = logical(db*0);
for i=1:(size(db,1)-1)
if db.INTERVENTION(i)==1 && isequal(db.SETTLEMENTDATE(i-1),db.SETTLEMENTDATE(i)) && isequal(db.DUID(i-1),db.DUID(i))
ind(i,:) = true;
end
end
db(ind) = [];
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