Multipanel graphing issue in Splus

I have a dataset of temperature means split by months and areas, and the number of years used to estimate each mean. I am trying to produce a multipanel split by area of mean vs. month with the number of years as a symbol. When I have the number of years formatted as double or integer, the symbols show up with two decimal places (i.e. 1.00 rather than 1). When I change the formatting to character or factor, the symbols do show up without the extra decimal places, but only five of the 12 months are plotted. Does anyone know why the graphs would be pared down to only 5 months when using factor or character as the format type?