x轴月核心图(iphone)

I would like to draw an XY graph using coreplot on iphone with date on x axis and some values on y axis. Referring to the DatePlot example shipping with the coreplot SDK, I was able to draw graph with date on x axis on a monthly scale (ie x ranges from 1 date of the month to last date). Now I want an yearly scale , ie I want to show All month names (Jan,Feb,Mar etc) on x axis and my tick inteval as one month time. I would like to draw an XY graph using coreplot