select a row from a matrix

Hei, How do I do the following task. I have a 90 x 12 matrix. From each three rows (1:3;4:6;7:9 etc.) I have to select one row. The condition is as follows.

If cell (2,12) < (1,12) and (2,9)>0 row 2 is selected.

But if then again cell (3,12) < 2,12) and (3,11) >0 row 3 is to be selected.

If however to start with (2,12) > (1,12) the first row is selected, and no comparison between (3,12) and (2,12) is to be considered.

Thanks in advance. Johannes

[Johannes Deelstra]

hei solved the problem no need for further attention Johannes

Answer 1

[Pritesh Shah]

a=ones(90,12);

j=1;

for i=1:3:87

if a(i+1,12)<a(i,12) & a(i+1,9)>0

b(j,:)=a(i+1,:);

elseif cond

b(j,:)=a(i+2,:);

else

b(j,:)=a(i,:);

end j=j+1;

end

[Johannes Deelstra]

thanks for the advice