2 vectors compare it

Hello, Ineed help with this question. I have 2 vectors to compare. Matrix below is a simplified vector with 2 columns that I want to compare. I want to move across the columns from column 1 to column 2 to column 1 continously till the end of the vector in an ascending order. If I move across , I record a value +ve, if I move within the same column, I record -ve. E.g

2 to 3 is +ve

3 to 4 is +ve

4 to 5 is +ve

5 to 7 is -ve( same column)

7 to 9 is -ve of -ve = +ve (same column movement)

9 to 10 is +ve

10 t0 12 is +ve

12 to 16 is +ve

16 to 17 is -ve

17 to18 is +ve

18 to 19 is +ve

19 to20 is +ve

[Dyuman Joshi]

You have skipped 12 to 15 and 15 to 16. Was that a mistake or intentional?

If it was intentional, what is the logic behind it?

[Joshua Folorunso]

Hi @Dyuman Joshi, Thank you for the notice. It was a mistake

[Stephen23]

The OP has modified this question multiple times, finally deciding that they will delete it entirely. Note to OP: this kind of behavior is not appreciated on this forum.

Backups of the main versions of this question:

9th Nov: https://web.archive.org/web/20221208181435/https://webcache.googleusercontent.com/search?q=cache:tidqiwwBxC8J:https://de.mathworks.com/matlabcentral/answers/1846708-comparing-between-and-within-columns-of-matrix

20th Nov: https://web.archive.org/web/20221208182039/https://webcache.googleusercontent.com/search?q=cache:pp4Uv8UcwhEJ:https://www.mathworks.com/matlabcentral/answers/1846708-comparing-between-and-within-columns-of-matrix&cd=1&hl=en&ct=clnk&gl=de

8th Dec: https://web.archive.org/web/20221208181514/https://webcache.googleusercontent.com/search?q=cache:hyiR1OPUmcoJ:https://www.mathworks.com/matlabcentral/answers/1846708-comparing-between-and-within-columns-of-3-vectors

https://web.archive.org/web/20221208182319/https://www.mathworks.com/matlabcentral/answers/1846708-2-vectors-compare-it

[Rena Berman]

(Answers Dev) Restored edit

Answer 1

[Matt J]

I will assume here that the oddity mentioned above by @Dyuman Joshi is an error in the presentation of the example.

A=[2   3
4   5
10  7
15  9
16  12
17  18
19  20];

A=A';
B=A*0+[1;2];

[~,is]=sort(A(:));

B=2*abs(diff(B(is))')-1  %result

B = 1×13

1 1 1 -1 -1 1 1 1 -1 -1 1 1 1

[Bruno Luong]

A variation without the need of B

A=[2   3
4   5
10  7
15  9
16  12
17  18
19  20];

[~,is] = sort(A(:));
Vesign = 2*abs(diff(is>size(A,1)))-1

Vesign = 13×1

1 1 1 -1 -1 1 1 1 -1 -1

[Dyuman Joshi]

According to the statement provided above, expectec output should have 12 values, instead of 13 that you have gotten.

[Bruno Luong]

You have 7 x 2 = 14 numbers, so 13 pairs of succesive numbers

2
3
4
5
7
9
10
12
15
16
17
18
19
20

@Dyuman Joshi has asked you miss the 12-15, 15-16 (you jump from 12-16, skipping 15) and you never answer why 15 is skipped.

[Joshua Folorunso]

@Bruno Luong,

It was a mistake. Thank you.

[Joshua Folorunso]

Thank you very much @Matt J. and @Bruno Luong. The answer is correct except that the 5th and 10th step should be positive because -ve of -ve gives +ve.

The 5 to 7 step gives -ve which is correct but 7 to 9 is -ve of previous -ve because the movement is still in the same column so it should be positive (+ve). The same applies to 16 to 17.

How can I easily correct this?

Thank you

[Matt J]

Perhaps as follows?

A=[2   3
4   5
10  7
15  9
16  12
17  18
19  20];

A=A';
B=A*0+[1;2];

[~,is]=sort(A(:));

B=cumprod(2*abs(diff(B(is))')-1)  %result

B = 1×13

1 1 1 -1 1 1 1 1 -1 1 1 1 1

[Joshua Folorunso]

Yes.

This is correct now. Thank you very much.

Answer 2

[Bruno Luong]

A=[2   3
    4   5
    10  7
    15  9
    16  12
    17  18
    19  20];

[As,is] = sort(A(:));
col = 1 + (is>size(A,1));
Vesign = 2*~~diff(col)-1;
Vesign = cumprod(Vesign);
Ves = string(Vesign);
Ves = repmat("+", size(Vesign));
Ves(Vesign<0) = "-";
S = As(1:end-1);
T = As(2:end);
col_S = col(1:end-1);
col_T = col(2:end);
T = table(S,T,col_S,col_T,Ves)

T = 13×5 table
    S     T     col_S    col_T    Ves
    __    __    _____    _____    ___

     2     3      1        2      "+"
     3     4      2        1      "+"
     4     5      1        2      "+"
     5     7      2        2      "-"
     7     9      2        2      "+"
     9    10      2        1      "+"
    10    12      1        2      "+"
    12    15      2        1      "+"
    15    16      1        1      "-"
    16    17      1        1      "+"
    17    18      1        2      "+"
    18    19      2        1      "+"
    19    20      1        2      "+"

[Joshua Folorunso]

Thank you very much. This is correct too.

Answer 3

[Joshua Folorunso]

@Bruno Luong,

I will.

It was a mistake while creating another question. I mistakenly edited old question.