Build array from descriptive data without a loop
显示 更早的评论
I want to go from
Array1 = [10,3,3;1000,178,4];
to
Array2 = [10;13;16;1000;1178;1356;1534];
without using
Idx2 = 1;
Array2 = zeros(sum(Array1(:,3)),1);
for Idx1 = 1:size(Array1,1)
Array2(Idx2:Idx2+Array1(Idx1,3)-1) = [Array1(Idx1,1),Array1(Idx1,1)+[1:Array1(Idx1,3)-1].*Array1(Idx1,2)];
Idx2 = Idx2+Array1(Idx1,3)-1;
end
Help?
采纳的回答
Array1 = [10,3,3;1000,178,4];
Array2 = cell2mat(arrayfun(@(Idx) Array1(Idx,1) + (0:Array1(Idx,3)-1).'*Array1(Idx,2), (1:size(Array1,1)).','uniform', 0))
2 个评论
Gabriel Stanley
2023-2-17
Walter Roberson
2023-2-17
You didn't ask for performance, you asked for not using a loop. For most operations (but not all, not if you know the right obscure forms), arrayfun and cellfun are slower than looping.
If you were looking for performance, then your existing code could be tweeked to take advantage of cumsum() instead of calculating the indices each time, and you could use the calculation I used instead of using [original, colon expression] list constructor.
更多回答（1 个）
Array1 = [10,3,3;1000,178,4];
Array2 = cumsum(Array1,2)
2 个评论
Walter Roberson
2023-2-17
Tthe third column is the number of elements to generate, with the difference being the second column, and the starting point being the first column.
Kevin Holly
2023-2-17
ah, thanks for pointing that out.
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