[R] How to create a "heatline" -- heatmap in one dimension?

Jim Lemon jim at bitwrit.com.au
Thu Oct 29 23:32:31 CET 2009

```On 10/30/2009 08:42 AM, Woolner, Keith wrote:
> Hi,
>
>
>
> I'm trying to create a "heatmap" that is just a line segment.  That is,
> a graphic that shows an interval and how a dependent variable varies
> along that interval, with the value of the dependent variable shown by
> color rather than on a y-axis.
>
>
>
> The image() function produces something close to what I'm envisioning,
> but rather than plotting color on a 2-D grid, I need a line where the
> color carries the information about the other dimension.  The following
> example code gives a visual approximation of what I'm going for (using
> image(), but by shrinking the y-axis down to make the result line-like):
>
>
>
> x<- c(1:100)
>
> y<- abs(40-x)
>
>
>
> my.col<- heat.colors(10)
>
> par(pin=c(par("pin")[1],.05))
>
> image(x, 1, as.matrix(y), ylim=c(1,1), col=my.col, xaxt="n",xlab="",
> yaxt="n", ylab="", fg="transparent")
>
>
>
>
>
> I will be generating several of these "heatlines" to plot on a 2-D grid,
> which will contain other information on it as well, and so also need to
> be able to add the lines to an existing plot.
>
>
>
> I've read the doc for stripplot(), contour(), image(), and checked the R
> Graph Gallery (http://addictedtor.free.fr/graphiques/) to try to find
> something similar, but haven't figured out the best way to do this,  I
> envision a function similar to segments(), where you can specify where
> the line should be drawn, the line width (lwd), and other graphical
> parameters, but where you can specify a vector of color values.
>
>
>
> Is there a package that has such functionality already, and if not, what
> would be most elegant way to approach it?  If it matters, I'm running R
> 2.9.1 on XP 32-bit.
>
>
>
Hi Keith,
Maybe color.scale.line in the plotrix package will do what you want.

Jim

```