Are Gadfly plots currently composable?
There is add_plot_element(), which can add stuff to an existing layer: xs = [0:0.1:pi] l = layer(x=xs, y=sin(xs)) add_plot_element(l, Guide.title("Now it has a title")) You can then plot the layer using plot(l), and invoke either draw or display to actually show something. Further down, there's a bunch of overloads that...
Gadfly for Julia, plotting multiple dimension in Bar Chart
If I understand the question right, you can generate the plot you're looking for (minus the change in alpha value for different months) with using DataFrames, Gadfly data = DataFrame() data[:DrinkType] =["Coke","Coke","Coke","Coke","Pepsi","Pepsi","Pepsi","Pepsi"] data[:Country] = ["UK", "US", "UK", "US","UK", "US", "UK", "US"] data[:Month] = ["April", "April", "March", "March","April", "April", "March", "March"]...
Plot real-valued function with variable parameters
See plotting functions and expressions in the Gadfly manual. For your example, something like plot([x->x^2+1, x->(x-4)+(x+3)], -2, 2) should do the trick using anonymous functions. It's not currently possible to do this with multivariate functions as far as I'm aware....