### R and colors from another dimension

I like to have a *"x vs. y"*- plot in which the symbol colors
represent a additional (or another :-) dimension z.

I’m sure that there are several ways to do that, however here is the way I
understand.

Assume that *x*, *y* and *z* have the same length *n* :

```
n <- length(y)
```

At first I generate a vector from *z* (*z* will give the color) in the interval *[0,1]*

```
zp <- z - min(z) ## zp starts from 0
zpp <- zp/max(zp) ## zpp ends at 1
```

If I now multiply *zpp* by *n* I get a nice index vector which can be used
together with the result produced by *colorRampPalette()*:

```
cf <- colorRampPalette(c("blue","yellow","red"))
```

*cf* is a function. It’s argument is the length of the color vector which should
be returned. Now put everything together:

```
plot(x,y,col=cf(n)[n*zpp])
```

Here is a complete example:

This is how it looks like:

HTH