If statement does not work

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Andrea Sbaragli
Andrea Sbaragli 2021 年 5 月 24 日
コメント済み: the cyclist 2021 年 5 月 25 日
I have a problem in populating correctly a table. Starting from A(mx4) and B(nx4), where m>n, I have to create C(mx4). According to the code whether the if statement it is not true 4 coloumn have default value.
function [Int12] = bundle(F1,F2)
A= zeros(height(F2), 8);
Int12= array2table(A);
Int12.A2 = NaT(length(A),1,'Format', 'dd-MMM-yyyy HH:mm:ss.SSSSSSSSS' );
Int12.A6 = NaT(length(A),1, 'Format', 'dd-MMM-yyyy HH:mm:ss.SSSSSSSSS' );
for i=1: height(F2)
Int12(i,5)= F2(i,2); % tag
Int12(i,6)= F2(i,1); % timestamp
Int12(i,7)= F2(i,3); % X
Int12(i,8)= F2(i,4); % Y
if abs(F2{i,1}- F1{j,1})<= duration('00:00:01.000000000')
Int12(i,1)= F1(j,2); % tag
Int12(i,2)= F1(j,1); % timestamp
Int12(i,3)= F1(j,3); % X
Int12(i,4)= F1(j,4); % Y
The problem is that the function works but at a certain point even if the if statement is true it does not work anymore.
  11 件のコメント
the cyclist
the cyclist 2021 年 5 月 25 日
It is no surprise to me that your code is computationally expensive. You are comparing 79329 elements to 47614 elements. That is simply a large number of comparisons.
Also, if all of your times were close to each other, you would be creating a table that is over 3 billion rows long (79329x47614). I don't know how big it will actually be, but I expect it is much larger than the memory you have preallocated.
You haven't really described the overall intent of your code. Do you really need to store every instance where a row of F2 is close in time to F1? Or maybe your output is actually something simpler and smaller.
What does the result need to be? It is possible that there is a faster way to do it.


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