How to remove repeating elements from an array

조회 수: 356 (최근 30일)
NS
NS 2011년 9월 25일
댓글: Life is Wonderful 2020년 4월 12일
Hi Guys,
I have two matrices X and Y of the same size. Each element in Y has a corresponding element in X. There are some repeating values in X (and correspondingly in Y as well). Is there any way to remove these elements from the matrices.
Thanks, NS
  댓글 수: 2
Hesham Hendy
Hesham Hendy 2014년 11월 22일
If I want to keep one value of repeated values without sorting, what can I do ???
Image Analyst
Image Analyst 2014년 11월 22일
Start a new question and give a small example.

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채택된 답변

UJJWAL
UJJWAL 2011년 9월 26일
Hi NS,
Ok. Now I understand what you want. ok. There is a way to do this. Take a look at the code below :
a = randi(10,[1,20]);
[b,m1,n1] = unique(a,'first');
[c1,d1] =sort(m1);
b = b(d1);
In this way your problem is solved. similarly you can also do so for the other matrix. Hope this helps...
Happy to help
UJJWAL
  댓글 수: 2
Andrei Bobrov
Andrei Bobrov 2011년 9월 26일
[a b] = unique([X;Y]','rows','first');
xyb = sortrows([a b],3)';
X = xyb(1,:);
Y = xyb(2,:);
NS
NS 2011년 9월 26일
Thanks. I figured it that day itself. :)

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추가 답변 (4개)

UJJWAL
UJJWAL 2011년 9월 25일
Use the unique function. Take the following example :-
a = randi(10,[1,20]) will display a 1 by 20 matrix of pseudorandom integers with uniform distribution in the range 1:10 . Obviously there will be repeated elements in the matrix. Suppose now you create a second matrix p = sin(a). So there is a mapping defined. Now type unique(a). It will give you only the unique values in a that is it will not display repeated values of the same element. Now type unique(p) : It will similarly display the unique values in p.
Hope it resolves your doubt
Best Wishes
Ujjwal
  댓글 수: 2
Jan
Jan 2011년 9월 25일
If you want to remove elements on the same positions in both matrices, you can use the 2nd and 3th output of unique. See "help unique".
NS
NS 2011년 9월 25일
Hi Ujjwal,
I dont want the order of the elements to be rearranged. When I use unique, the elements are arranged in an ascending order.
Eg. if X=[0 13 18 22 22] and Y=[0 1 -1 3 3]
I want my output to be as X=[0 13 18 22] and Y=[0 1 -1 3]
How do I do that

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Fangjun Jiang
Fangjun Jiang 2011년 9월 26일
For duplicated x-y pairs, if you want to keep the last one:
X=[0 13 22 18 22 22 10];
Y=[0 1 3 -1 3 3 -1];
A=[X;Y]';
[UniXY,Index]=unique(A,'rows');
DupIndex=setdiff(1:size(A,1),Index);
A(DupIndex,:)=[];
X=A(:,1)'
Y=A(:,2)'
X =
0 13 18 22 10
Y =
0 1 -1 3 -1
If you want to keep the first one, use:
[UniXY,Index]=unique(A,'rows','first');
  댓글 수: 1
Aidin Golrokh
Aidin Golrokh 2018년 7월 18일
For a big matrix, this code will produce repeating numbers.

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SIVAKUMAR KARURNKARAN
SIVAKUMAR KARURNKARAN 2015년 5월 20일
function B=adjacentmat(n,e) R=combntns(1:n,2); k=1:e; r=nchoosek(n,2); B=zeros(n,n,r,r);
for i=1:r for j=1:r R([i j],:)=R([j i],:); F=R(k,:); A=zeros(n,n); for m =1:e; A(F(m,1),F(m,2))=1; A(F(m,2),F(m,1))=1;
end
B(:,:,i,j)=A;
end
end
return in this output has more duplicate matrices i want only distinct matrices. i need the code of comparing the matrices and find which is distinct

Ismet Ozturk
Ismet Ozturk 2018년 3월 29일
편집: Ismet Ozturk 2018년 3월 29일
function [ a ] = deleteRepetation( a )
leng=size(a);tempa=zeros(1,2);
for i=1:leng(1)
tempa=a(i,:);
tempa=sort(tempa);
a(i,:)=tempa;
end
deletionList=[1];
while size(deletionList)>0
deletionList=[];leng=size(a);
for i=1:leng(1)
tempa=a(i,:);
for j=i+1:leng(1)
if tempa==a(j,:)
deletionList=[deletionList j];
end
end
end
a(deletionList,:)=[];
end
  댓글 수: 1
Life is Wonderful
Life is Wonderful 2020년 4월 12일
Couple of things noted and suggestion added for the above code
Code point-1
tempa=sort(tempa);
Replace with
tempa=sortrows(tempa);
Code point-2
if tempa==a(j,:) %might NOT always work for Tables
Replace with
if isequal(tempa,a(j,:)) % better implementation

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