Plot one or more rectangles with rounded corners.

## Arguments

- x1, y1
x and y coordinates of the bottom left corner

- x2, y2
x and y coordinates of the top right corner

- xr, yr
the proportion of length of a side of the rectangle, from which the rounded corners start. Values between 0 and 1 are permitted. See details.

- n
the number of points used to approximate the curvature of the rounded corner

- ...
other parameters passed to [graphics::polygon()].

## Details

The rounded corner is a part of a circle (one quarter) drawn between two points of neighbouring sides of a rectangle. The relative position of these two points determine how rounded will the final shape be. The position of these points is determined by the parameters `xr` and `yr`, which determine the proportion of side x and y, from which the rounded corner is drawn. Values between 0 and 1 are permitted, but given the symmetricity of a rectangle, values larger than 0.5 are reflected back (modulo 0.5). When both xr and yr are 0 or 1, normal rectangle without rounded corners is drawn. When xr and yr are 0.5, ellipsis is drawn.