You need to learn how to index into a matrix using a single index. This is just the number of the element in terms of how it is stored in memory. MATLAB stores a 2-d array in order, going down the columns. So the elements in column 1 are the first 7 elements in memory, then come the elements of column 2, etc. So if you extracted elements [4 10 16] from the array, you would get
matrix([4 10 16])
ans =
22 16 10
We get this result simply enough by recognizing that the 4th element in memory is the (4,1) element, thus from the first column. If your matrix is NxM, then this computation is simply
singleindex = rowindex + (columnindex-1)*N
Read the help for sub2ind, if you don't want to bother doing the computations (they are trivial as you can see) yourself.
