Finding all the subsequences

I have a set of numbers.I pollted it.I need to find all the subsequence of it and need to plot

If a=[1,2,3,4,5,6,7,8,9,0.4,0.1,0.23]

subsequence like{'1:2,2:3,3:4,.........'}

How can I do this,and I need to find a point (suppose 2)in the graph or not then marking that point in that subsequence.I am new in matlab.Please help me.