user specified tick positions.
Right now the ticks are auto generated at specified places according to number of grid.
I would like to specify the ticks are arbitrary spacings.
For example. My solar radiation of the year plot shows days on the xaxis with ticks at 0, 29,57,85 to 365
I would like the ticks to be at 0,31,59,90. that way i can gride the xaxis in months by showing days.