How can I remove double values in an array

i have these set of two arrays A and B,

A=

[4, 3.40 ;

6, 3.20;

7, 5.50 ;

9, 6.13;

11, 7.18;

14, 8.23;

15, 9.28;

18, 10.33;

20, 11.38 ]

B = [

1, 0 ;

2, 0;

3, 0;

4, 0 ;

5, 0 ;

6, 0 ;

7, 0;

8, 0;

9, 0 ;

10, 0 ;

11, 0;

12, 0;

13, 0;

14, 0;

15, 0;

16, 0;

17, 0;

18, 0;

19, 0 ;

20, 0 ]

and I concatenate them to get C:

C = [

1, 0;

2, 0;

3, 0;

4, 3.40;

4, 0;

5, 0;

6, 3.20;

6, 0;

7, 5.50;

7, 0;

8, 0;

9, 6.13;

9, 0;

10, 0;

11, 7.18;

11, 0;

12, 0;

13, 0 ;

14, 8.23;

14, 0 ;

15, 9.28;

15, 0;

16, 0;

17, 0;

18, 10.33;

18, 0;

19, 0;

20, 11.38 ;

20, 0 ]

The first array contains subsets of the second array. Please how can I remove the rows in C that has zero in the second column.

Thanks

Answer 1

[Voss]

It's better to build C the way you want it from the start:

A=[4,  3.40 ;
  6, 3.20; 
  7, 5.50 ;
  9,  6.13; 
  11,  7.18; 
  14,  8.23; 
  15,  9.28; 
  18,  10.33; 
  20,  11.38 ];
B = [  
  1,  0 ; 
  2,  0;
  3, 0;  
  4,  0 ; 
  5,  0 ; 
  6,  0 ; 
  7,  0;  
  8,  0;  
  9,  0 ; 
  10,  0 ; 
  11,  0;  
  12,  0;  
  13,  0;  
  14,  0;  
  15,  0; 
  16,  0;  
  17,  0;  
  18,  0; 
  19,  0 ; 
  20,  0 ];

C = B;
[ism,idx] = ismember(A(:,1),B(:,1));
C(idx(ism),2) = A(ism,2);

disp(C);

    1.0000         0
    2.0000         0
    3.0000         0
    4.0000    3.4000
    5.0000         0
    6.0000    3.2000
    7.0000    5.5000
    8.0000         0
    9.0000    6.1300
   10.0000         0
   11.0000    7.1800
   12.0000         0
   13.0000         0
   14.0000    8.2300
   15.0000    9.2800
   16.0000         0
   17.0000         0
   18.0000   10.3300
   19.0000         0
   20.0000   11.3800

[Voss]

Or starting from the C you have already (which is posted in your question), here's a way to remove rows whose first element is a duplicate and whose second element is 0:

C = [  
  1,  0; 
  2,  0; 
  3,  0; 
  4,  3.40; 
  4,  0; 
  5,  0; 
  6,  3.20; 
  6,  0;
  7,  5.50; 
  7,  0; 
  8,  0; 
  9,  6.13; 
  9, 0; 
  10,  0; 
  11,  7.18; 
  11,  0; 
  12, 0; 
  13,  0 ;
  14,  8.23; 
  14,  0 ;
  15,  9.28; 
  15,  0; 
  16,  0; 
  17,  0; 
  18,  10.33; 
  18,  0; 
  19,  0;
  20,  11.38 ;
  20,  0 ];

idx = diff(C(:,1)) == 0;
idx = [false; idx] | [idx; false];
C(idx & C(:,2) == 0,:) = [];

disp(C);

    1.0000         0
    2.0000         0
    3.0000         0
    4.0000    3.4000
    5.0000         0
    6.0000    3.2000
    7.0000    5.5000
    8.0000         0
    9.0000    6.1300
   10.0000         0
   11.0000    7.1800
   12.0000         0
   13.0000         0
   14.0000    8.2300
   15.0000    9.2800
   16.0000         0
   17.0000         0
   18.0000   10.3300
   19.0000         0
   20.0000   11.3800

[TTA]

Thank you very much

[Voss]

You're welcome!

Answer 2

[MarKf]

"remove rows in C that has zero in the second column" so pretty much the array B but with the 2nd column values of A whenever their 1st column values match? if that's the case:

A = [4,  3.40 ;  6, 3.20;   7, 5.50 ;  9,  6.13; ];
B = [(1:10)', zeros([10 1])];
C = B;
C(ismember(B(:,1),A(:,1)),2)=A(:,2)

C = 10×2

1.0000 0 2.0000 0 3.0000 0 4.0000 3.4000 5.0000 0 6.0000 3.2000 7.0000 5.5000 8.0000 0 9.0000 6.1300 10.0000 0

Though I guess that works only if the values in A's 1st column are all contained in B's 1st column. Otherwise you can specify:

C(ismember(B(:,1),A(:,1)),2)=A(ismember(A(:,1),B(:,1)),2);

[TTA]

Thank you very much