The Philosophy of the tool determines How Good it is

The core of the ggplot2 is the graph model, which lattice is lack of. When I use the xyplot in the lattice, if some changes are needed, I need to delete the original parameter settings or copy the code to make a new one. But in ggplot2, after getting a original object of graph, we can adding or overwrite the previous settings with little effort. The reason is that ggplot2 support this, since the grammar is designed to make it easy and avoid duplication.

Maybe this reflects the author's deeper understanding or philosophy of the creating plot - iterative creating something, not at one time. I believe the implementation complexity of Lattice is not less than ggplot2. But the usability of Lattice is poor compared with ggplot2. The philosophy really makes tools difference.