# How can I check if the columns of my matrix have value in common?

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Agnese Chini on 26 Sep 2021
Answered: yanqi liu on 27 Sep 2021
Hi, I have a basic problem.
I have a matrix 7x21 double and I want to compare each column with the others. I want to understand if a value in the first column is repeated in the following 20 columns. Either a value from the sixth column in all five first or subsequent columns.

Walter Roberson on 26 Sep 2021
I am not certain what you are asking
Either a value from the sixth column in all five first or subsequent columns.
M = randi(2, 10, 8)
M = 10×8
2 1 1 2 1 2 2 1 1 2 1 1 1 1 2 1 1 2 1 2 1 2 1 1 1 2 1 2 1 1 2 1 1 1 1 2 2 2 2 1 2 2 2 1 2 1 1 1 2 2 2 2 2 2 1 1 2 2 2 2 2 2 2 1 2 2 2 1 2 1 1 1 2 2 2 2 1 1 2 2
sum(M(:,6) == M(:,1:5), 2) == 5
ans = 10×1 logical array
0 0 0 0 0 0 1 1 0 0
Walter Roberson on 26 Sep 2021
When you ask "which" you might be asking what the location is, or you might be asking what the value is. My code returns 0 for locations that do not match and 1 for ones that match, so it answers the question about location.
any(matches, 2)
is 1 for rows that match.
to_compare(any(matches, 2))
will tell you the values but not the location

yanqi liu on 26 Sep 2021
sir，may be use the follow code
clc
close all
clear all
% init matrix
M = randi([1 100], 10, 8)
M = 10×8
7 36 81 22 55 59 50 4 74 14 62 38 7 3 78 43 7 38 43 90 12 11 7 53 38 10 58 46 90 4 37 3 33 29 93 20 98 8 30 36 59 26 84 36 100 6 56 96 13 56 68 25 51 39 42 69 38 19 89 23 1 96 33 49 24 100 84 39 41 50 39 64 55 86 48 44 9 12 48 72
% choose one column
use = 4;
% find value
Mu = M(:, use)
Mu = 10×1
22 38 90 46 20 36 25 23 39 44
M2 = M;
M2(:, use) = NaN;
% the different range
th = 0;
for i = 1 : length(Mu)
mi = Mu(i);
di = abs(M2 - mi);
[r, c] = find(di <= th);
fprintf('\n\nthe %d data of column %d is %d\n', i, use, mi);
if length(r) < 1
fprintf('\n can not find other column has this value!');
end
for j = 1 : length(r)
fprintf('\nM(%d,%d)=%d', r(j), c(j), M(r(j), c(j)));
end
end
the 1 data of column 4 is 22
can not find other column has this value!
the 2 data of column 4 is 38
M(4,1)=38 M(8,1)=38 M(3,2)=38
the 3 data of column 4 is 90
M(4,5)=90
the 4 data of column 4 is 46
can not find other column has this value!
the 5 data of column 4 is 20
can not find other column has this value!
the 6 data of column 4 is 36
M(1,2)=36 M(5,8)=36
the 7 data of column 4 is 25
can not find other column has this value!
the 8 data of column 4 is 23
can not find other column has this value!
the 9 data of column 4 is 39
M(7,6)=39 M(9,7)=39
the 10 data of column 4 is 44
can not find other column has this value!
fprintf('\n');
##### 2 CommentsShowHide 1 older comment
Agnese Chini on 26 Sep 2021
for i = 1 : length(Mu)
mi = Mu(i);
di = abs(M2 - mi);
[r, c] = find(di <= th);
fprintf('\n\nthe %d data of column %d is %d\n', i, use, mi);
if length(r) < 1
fprintf('\n can not find other column has this value!');
else
fprintf('\n I find the same value in here!'); %I want to know where is it the same value and wich is the value
end
for j = 1 : length(r)
fprintf('\nM(%d,%d)=%d', r(j), c(j), M(r(j), c(j))); %What did you print here?
end
end

yanqi liu on 27 Sep 2021
clc
close all
clear all
% init matrix
M = randi([1 100], 10, 8)
M = 10×8
85 51 44 55 49 2 1 73 5 99 30 99 77 99 6 50 6 92 97 49 35 57 24 44 27 96 96 45 69 8 89 94 64 29 82 78 13 89 77 9 1 41 53 91 33 87 12 30 52 64 85 17 54 62 63 58 74 64 21 94 28 87 80 16 56 58 77 16 59 28 94 91 96 83 2 84 54 64 39 1
% choose one column
use = 4;
% find value
Mu = M(:, use)
Mu = 10×1
55 99 49 45 78 91 17 94 16 84
M2 = M;
M2(:, use) = NaN;
% the different range
th = 0;
for i = 1 : length(Mu)
mi = Mu(i);
di = abs(M2 - mi);
[r, c] = find(di <= th);
fprintf('\n\n the %d data of column %d is %d\n', i, use, mi);
if length(r) < 1
fprintf('\n can not find other column has this value!');
continue;
else
fprintf('\n I find the same value in here! Please view the follow %d data for detail!', length(r));
end
for j = 1 : length(r)
fprintf('\n M(%d,%d)=%d', r(j), c(j), M(r(j), c(j)));
end
end
the 1 data of column 4 is 55
can not find other column has this value!
the 2 data of column 4 is 99
I find the same value in here! Please view the follow 2 data for detail!
M(2,2)=99 M(2,6)=99
the 3 data of column 4 is 49
I find the same value in here! Please view the follow 1 data for detail!
M(1,5)=49
the 4 data of column 4 is 45
can not find other column has this value!
the 5 data of column 4 is 78
can not find other column has this value!
the 6 data of column 4 is 91
I find the same value in here! Please view the follow 1 data for detail!
M(9,8)=91
the 7 data of column 4 is 17
can not find other column has this value!
the 8 data of column 4 is 94
I find the same value in here! Please view the follow 2 data for detail!
M(9,7)=94 M(4,8)=94
the 9 data of column 4 is 16
I find the same value in here! Please view the follow 1 data for detail!
M(8,8)=16
the 10 data of column 4 is 84
can not find other column has this value!
fprintf('\n');

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