MATLAB: Finding distinct values in a column of a matrix

distinct valuesunique value in column of a matrix

I have a 81*4 matrix. I want to find the distinct values only in the first column, which can also be seen as the first column of every row.

eg: a= 2 3

     4 3
     4 5
     2 3

ans should be = 2

unique() is of no use here, it supports only whole row distinction.

unique( a(:,1) )

variant

o34 = zeros(size(I));
o34(3,4)=1;
o34d = bwdist(o34);
distato34 = [I(I~=1) o34d(I~=1)]

more variant

o = [3 4];
dC = arrayfun(@(x)(cumsum(ones(size(I)),x)-o(x)).^2,1:2,'un',0);
d = sqrt(dC{1} + dC{2});
l = I~=1;
out = [I(l) d(l)]

more more variant

[Hi Hj] = find(I~=1);
out = [I(I~=1) sqrt(sum(bsxfun(@minus,[Hi Hj],[3 4]).^2,2))]

b = sortrows(a,2);