I am thinking of drawing a graph that will illustrate fluctuation of an average for each day of a month. This part is easy with Plot. On top of drawing line graph to present average values for each day I would also like to calculate mean value of my data in the following way: 1st day - mean of average for day 1, 2nd day - mean of average for days 1 and 2, etc. After reading docs for transformations and several tries I am not sure if Plot is currently capable to do it. What are you thoughts?

I think I need more than window transform (I already tried this one before posting my question). Window transform has width option, but as far as I know it can only take integer as value, unless I am missing something here. I think a function that will be evaluated for each of my data points, where I could calculate mean value from n-th integration will be what I need.