[R] adjusting levelplot color scale to data

[David Winsemius]

On Nov 7, 2011, at 12:10 AM, David Winsemius wrote:

>
> On Nov 6, 2011, at 10:08 PM, Lanna Jin wrote:
>
>> Hi guys,
>>
>> I have a matrix with values varying from approximately -0.7 to 0.33  
>> that I
>> want to create a heatmap/levelplot with.
>>
>> When I execute the levelplot function for my matrix, I end up  
>> getting colors
>> that are adjusted to the max and min rather than around 0. In other  
>> words,
>> ideally I would like to have a color ramp that goes from red  
>> (negative
>> number), to white (0), to blue (positive); however, right now the  
>> value 0 is
>> in the blue.
>>
>> Any insight on how to address this problem?
>
>
> ?levelplot  # which leads to"
> ?level.colors  # which in turn leads to:
> ? colorRamp
>
color.palette =    colorRampPalette(c("red", "white", "blue"))
> levelplot(as.matrix(dat), at=seq( -.8, .4, length=31),  
> col=color.palette(30) )
>
>
> And next time, please post the output of dput rather than a mangled  
> print() output.
> -- 
> David.
>>
>> Thanks in advance!
>>
>> example...
>> my matrix "y" looks something like this
>>                A                 B                      C
>> D                    E
>> row1         -0.5046406 -0.021579587    -0.4419101 -0.2999195330
>> -0.4845047
>> row2         -0.3070091 -0.059065936     0.3329806 -0.0519335420
>> -0.5766368
>> row3         -0.7271707  0.073282855    -0.3181990 -0.2485017700
>> -0.5732781
>> row4          0.3329806 -0.017762750    -0.1513197 -0.1016354970
>> 0.2528442
>>
>> levelplot(y) yields a color scale from red (-0.8 to 0.2) to blue  
>> (0.2 to
>> 0.4)
>> I'd want the color scale to be from red (-0.8 to 0) to blue (0 to  
>> 0.4)
>>
>>
>>
>> -----
>> Lanna
>> --
>> View this message in context: http://r.789695.n4.nabble.com/adjusting-levelplot-color-scale-to-data-tp3997342p3997342.html
>> Sent from the R help mailing list archive at Nabble.com.
>>
>> ______________________________________________
>> R-help at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>
> David Winsemius, MD
> West Hartford, CT
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

David Winsemius, MD
West Hartford, CT