Flipping the Y axes in Matlab

In most computer graphics APIs/toolkits, the default Y direction is from top to bottom, i.e. the Y origin (y = 0) is the top and increases as it goes downward. However in most scientific plots, the Y direction is the opposite. The positive Y direction is upwards.
Because of this discrepancy, there is always confusion when drawing images, especially in Matlab (e.g. imagesc). While one possibility would be to flip the data array via flipud, my preferred method is to use the 'ydir' option.

set(gca, 'ydir', 'normal');

This leaves the data as is, no flipping data, and only changes the the plot options, which separates data from presentation. (Model/View)
An interesting point is that the default value for ydir is 'reverse' which is the default direction of most graphics packages.