Implementing custom graphics in Stata

Stata provides a fairly extensive set of graphs. However sometimes users need to implement custom graphs, which are not yet available. In some cases it is possible to “tweak” a standard graph so that it results in the desired image; in other cases it is not possible. Stata uses complex system of objects implemented as classes and heavily relies on inheritance, polymorphism and overriding to implement its graphics. While standard class programming is well described in the Stata manuals, the particulars of the design and implementation of the Stata graphics features are not documented by developers and thus are not easily accessible. We will: briefly discuss the overall idea of how Stata graphics works, review a couple of examples of custom graphic commands and their implementation. This part of discussion will be most useful for skilled Stata programmers that want to know what is happening under the hood and, perhaps, optimize their graphic commands to improve performance or add features. After that we will look at the new command -matrixplot-, the sample images rendered by which generated quite a lot of interest in statalist. -matrixplot- can be used to produce contour plots, heatmap-like plots, particularly useful when working with climate data, as well as displaying raster images for digital image processing.