how to delete repeated rows in a table?

I have an array M below. There are some repeated values in column 1. I would like to write a code that deletes all the rows that have repeated values in column 1. The final answer should be [518640 5.959; 522225 8.988].

This is a sample dataset. My actual data has more than 50,000 rows, and I need to delete all the repeated data. Thanks.

M = [518460 3.322; 518460 -12.984; 518520 3.798; 518520 -10.28; 518580 7.763; 518580 16.851; 518640 5.959; 522225 8.988];

Answer 1

[per isakson]

Test this

%%
M = [518460 3.322; 518460 -12.984; 518520 3.798; 518520 -10.28; 518580 7.763; 518580 16.851; 518640 5.959; 522225 8.988];
%%
[~,ixu] = unique( M(:,1), 'stable' );
M(ixu,:)

ans = 5×2

1.0e+05 * 5.1846 0.0000 5.1852 0.0000 5.1858 0.0001 5.1864 0.0001 5.2222 0.0001

In response to comment

If everything fails, try a for-loop

for jj = 1 : size(M,1)
    ixm = find( M(jj,1) == M(:,1) );
    if numel(ixm) >= 2
        M(ixm,1) = nan;
    end
end
M( isnan(M(:,1)), : ) = []

M = 2×2

1.0e+05 * 5.1864 0.0001 5.2222 0.0001

[Jayden Yeo]

The above code only remove one instance of the repeating values in column 1.

M = [518460 3.322;

518460 -12.984;

518520 3.798;

518520 -10.28;

518580 7.763;

518580 16.851;

518640 5.959;

522225 8.988];

Based on the matrix M above, how should the code be modified if I would like the final answer to be

[518640 5.959; 522225 8.988]?

[per isakson]

See response in the answer.

[Jayden Yeo]

Thanks a lot.

Answer 2

[Walter Roberson]

format long g
M = [518460 3.322; 518460 -12.984; 518520 3.798; 518520 -10.28; 518580 7.763; 518580 16.851; 518640 5.959; 522225 8.988]

M = 8×2

1.0e+05 * 5.1846 0.0000 5.1846 -0.0001 5.1852 0.0000 5.1852 -0.0001 5.1858 0.0001 5.1858 0.0002 5.1864 0.0001 5.2222 0.0001

[~, ia] = unique(M(:,1), 'stable');
M = M(ia,:)

M = 5×2

1.0e+05 * 5.1846 0.0000 5.1852 0.0000 5.1858 0.0001 5.1864 0.0001 5.2222 0.0001