An extension to 'ggplot2' with miscellaneous functions. It contains two groups of functions: Functions in the first group draw 'ggplot2' - based plots: gg_shading_bar() draws barplot with shading colors in each bar. geom_rect_cm(), geom_circle_cm() and geom_ellipse_cm() draw rectangles, circles and ellipses with centimeter as their unit. Thus their sizes do not change when the coordinate system or the aspect ratio changes. Functions in the second group generate coordinates for regular shapes and make linear transformations.