If you want to get the rows of an array (x) with 0 on column 1, you do x[x[,1]==0]. basically, x[,1] gives you a one column table with the appropriate column, x[,1]==0 gives you a vector of true,false values, which you can use to index into the array again.

While that does pull out the rows which have 0 in column 1, it packs those return values into a vector (the first element of each of the selected rows, followed by the second element of the selected rows, etc.). If you want to extract those rows of the matrix, and keep them in matrix form, then this will do it (note the extra comma):

x[x[,1]==0,]

Yes, R is pretty nice in that sense. Matlab can do many of the same tricks, e.g. the Matlab equivalent of my command above is

x(x(:,1)==0,:)

Matlab doesn't have a simple way to do your version that I know of, since Matlab doesn't automatically recycle a vector index to a matrix. You'd have to do something like x(repmat(x(:,1)==0,n,1)) where n is the number of columns in x -- or to avoid hardcoding the n, you could do x(repmat(x(:,1)==0,size(x,2),1)) which is starting to get ugly isn't it?