adjusting axis labels NVD3 graph in rCharts

I am using the rCharts nPlot() function to display stacked or grouped bar charts given contingency table type data. The "multiBarChart" is displayed in a shiny application. A piece of the code that I use in my shiny application is given below.

    graphData <- reactive({    as.data.frame(table(eval(inputVar1()),eval(inputVar2())))    })    output$myChart <- renderChart({    p1 <- nPlot(Freq ~ Var1, group="Var2", data=graphData(), type="multiBarChart")    p1$addParams(dom='myChart')    return(p1)    })

In my dataset, one categorical variable has 16 levels. When this variable is displayed along the x-axis of the "multiBarChart", not all labels are shown. Is there a way in nPlot to adjust the font size of axis labels? I'm thinking something like cex.axis=0.5 or cex.lab=0.5 or something like that.

Alternatively, is there a parameter like las= which would allow me to rotate the axis label 90 degrees and perhaps have a cleaner plot where all labels of categorical variables are displayed along the x-axis of the plot.

Any advice the group could provide is greatly appreciated!!