plotting of graphs from different time and data files

I am trying to plot a graph of wind velocity against time.

I have two different kinds of files. One of them consists of daily data, and the other one consists on monthly data.

I have successfully plot ONE DAY of data against daily hours, and ONE month of data against date.

I encountered two problems:

• The ONE MONTH data I plotted showed only 'Feb 1' and 'Mar 1', and did not show any date graduation in between (I used 'datetick' already).
• How can I link these data form different .mat files and plot them on the same graph time accordingly?

Please help :((