Eliminate a row where a column has repeated values

Hi I have the following matrix

eliti =

Columns 1 through 8

         0         0    1.0000         0         0         0         0         0
         0         0    1.0000         0         0         0         0         0
         0    1.0000         0    1.0000    1.0000         0         0         0

Columns 9 through 16

         0         0         0         0         0    1.0000    1.0000         0
    1.0000    1.0000         0         0         0         0    1.0000         0
         0         0         0         0         0         0    1.0000         0

Columns 17 through 21

-24.0000   38.0000   10.0751    0.0413    0.2388
-52.0000   26.0000   11.1629    0.0458    0.6012
-24.0000   38.0000   10.0751    0.0413    0.3106

And I need to eliminate where there a repeated values in the 18th column so it will be like this eliti =

Columns 1 through 8

         0         0    1.0000         0         0         0         0         0
         0    1.0000         0    1.0000    1.0000         0         0         0

Columns 9 through 16

    1.0000    1.0000         0         0         0         0    1.0000         0
         0         0         0         0         0         0    1.0000         0

Columns 17 through 21

-24.0000   38.0000   10.0751    0.0413    0.2388
-52.0000   26.0000   11.1629    0.0458    0.6012

Answer 1

[Andrei Bobrov]

[~,b] = unique(eliti(:,18),'stable');
eliti_new = eliti(b,:);

Answer 2

[Chad Greene]

You can use the indices returned by unique to get the rows corresponding to unique values in column 18:

M = randi(5,[3 21])
[~,ia] = unique(M(:,18))
M_new = M(ia,:);