I created this schedule while experimenting with my second round of marathon training.  Both plans work but the number of running days are different.  I found my training was going smoother with an extra day of run/walking.  I felt my legs were looser and in turn my runs were easier and felt less forced.   

In this schedule I do not include the run/walk intervals as to not confuse with the fourth day of running which is ALWAYS a walk/run regardless. Again, you can add the run/walk intervals to all of these runs.

I recommend giving yourself one month to work up to 3 miles before following a marathon training schedule. These schedules are based on already being able to run or run/walk 3 miles.