(This article was first published on

A contour plot is a simple way to plot a surface in two dimensions. Lines with a constant Z value are plotted on the X-Y plane.Typical uses include weather maps displaying "isobars" (lines of constant pressure), and maps displaying lines of constant elevation useful in, e.g., hiking. Unusual examples include maps of constant travel time, for example this map, which transforms space so that
**SAS and R**, and kindly contributed to R-bloggers)To

**leave a comment**for the author, please follow the link and comment on his blog:**SAS and R**.R-bloggers.com offers

**daily e-mail updates**about R news and tutorials on topics such as: visualization (ggplot2, Boxplots, maps, animation), programming (RStudio, Sweave, LaTeX, SQL, Eclipse, git, hadoop, Web Scraping) statistics (regression, PCA, time series, trading) and more...