R help - Dec 2006 - heatmap with levelplot?

Hi,

How do I anchor z=0 to the white color in a levelplot so that
the color changes from cyan to magenta precisely as
z changes from negative to positive? Also is it easy to change
color scheme, say to blue/red as it's more dramatic? Is there a
better function for showing heatmap with a color bar?

Thanks in advance for any help, I've played with image,
heatmap and levelplot a little and haven't gotten very far.

Yuli Zhou

On 12/22/06, Yuli Zhou <yul.zhou at gmail.com>
wrote:
> Hi,
>
> How do I anchor z=0 to the white color in a levelplot so that
> the color changes from cyan to magenta precisely as
> z changes from negative to positive?
The changepoints are defined by 'at', and the colors are chosen more
or less linearly, so you need to make sure 0 is near the center of
your 'at'. E.g.

levelplot(cor(mtcars), at = seq(-1.01, 1.01, length = 20))

> Also is it easy to change
> color scheme, say to blue/red as it's more dramatic?
Sure, e.g.

bluered = colorRampPalette(c("red", "white",
"blue"), space = "Lab")
levelplot(volcano, col.regions = bluered(100), cuts = 99)

> Is there a
> better function for showing heatmap with a color bar?
>
> Thanks in advance for any help, I've played with image,
> heatmap and levelplot a little and haven't gotten very far.
>
> Yuli Zhou
>
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