Using FIND for common elements WITHOUT a loop (Vectorized?)

조회 수: 1(최근 30일)
Dave 2019년 2월 2일
댓글: Omar Salah 2020년 4월 11일
I have an array A 100x1 with different datenum that
I need to find in a big array B 5000000x1 (all datenum in B are in A, just repeated many times)
and then replace w another datenum C 100x1 (same index as A)
I am using find( ) but it is taking too long. Is there a way to do this without a loop?
BB=B %making a copy of B to check after.
for i=1:size(A,1)
  댓글 수: 2
Dave 2019년 2월 3일
thank you, I don't know how to take your comment as the accepted answer.

댓글을 달려면 로그인하십시오.

채택된 답변

Stephen 2019년 2월 3일
Use ismember and its second output argument:
>> A = randperm(5)
A =
3 5 4 1 2
>> B = randi(5,1,9)
B =
5 1 2 5 1 2 4 5 4
>> C = (1:5).^2
C =
1 4 9 16 25
>> [~,X] = ismember(B,A);
>> BB = C(X)
BB =
4 16 25 4 16 25 9 4 9
  댓글 수: 3
Omar Salah
Omar Salah 2020년 4월 11일
Hi Stephen, I really wanted to thank you. I wanted to imporve my really slow code in which I tryz to find a 100k elements in a 320k elements vector. using is memeber the code runs in 5.4832 seconds instead of 1170 seconds when using for and parfor. Vectorization is magical for Big data.

댓글을 달려면 로그인하십시오.

추가 답변(0개)

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by