[R] Help with color.scale {plotrix}

[Sarah Goslee]

Hi Kumar,

You're overthinking it:

in RGB, colorspace, cs1 is red, cs2 is green, cs3 is blue.
So if cs1=c(1,1),cs2=(c(0,1),cs3=0 (or c(0,0) because of R's recycling)
the first color in the sequence is c(1, 0, 0) or red ##FF0000 and the
second color is c(1, 1, 0) #FFFF00 or yellow.

Sarah

On Fri, Oct 9, 2015 at 11:16 AM, Kumar Mainali <kpmainali at gmail.com> wrote:
> Hi Jim,
>
> Thank you! Your color code does work. I still do not understand how red to
> yellow in RGB space translates to cs1=c(1,1),cs2=(c(0,1),cs3=0. In other
> words, I have RGB values for red and yellow. How do I go from there to the
> code you sent?
>
> Another question: some of my matrices have missing cells and I do not want
> to assign any colors to the missing cells. The following code gives me
> error. I am trying to use the output (cellcol) to the
> function color2D.matplot.
>
>> cellcol<-matrix("#000000", nrow=nrow(plotdata),ncol=ncol(plotdata))
>> cellcol[x<0.33]<-color.scale(x[x<0.33],c(1,0.8),c(0,0.8),0, na.color=NA)
> Error in cellcol[x < 0.33] <- color.scale(x[x < 0.33], c(1, 0.8), c(0,  :
>   NAs are not allowed in subscripted assignments
> In addition: Warning messages:
> 1: In min(x) : no non-missing arguments to min; returning Inf
> 2: In max(x) : no non-missing arguments to max; returning -Inf
> ᐧ
>
> Postdoctoral Associate
> Department of Biology
> University of Maryland, College Park
>
> On Fri, Oct 9, 2015 at 7:24 AM, Jim Lemon <drjimlemon at gmail.com> wrote:
>
>> Hi Kumar,
>> The color.scale function translates numeric values into one or more
>> intervals of color by a linear transformation into the numeric values that
>> specify colors. One of three color spaces (rgb, hcl and hsv) can be
>> specified, and the endpoints can be specified as "extremes=c(<minimum
>> color>,<maximum color>" or as three vectors of numbers. By default, the RGB
>> color space is used, so:
>>
>> # starts at RGB #FF0000 and finishes at RGB #FFFF00
>> red to yellow - extremes=c("red","yellow") OR cs1=c(1,1),cs2=(c(0,1),cs3=0
>> # starts at RGB #FFFF00 and finishes at RGB #00FF00
>> yellow to green - extremes=c("yellow","green") OR
>> cs1=c(1,0),cs2=(c(1,1),cs3=0
>>
>> Obviously the shades of colors that you want may differ from the above, so
>> you have to play with the values to get the ones you want. In many cases,
>> you will have to specify more than two numbers for the color specs to get
>> the "in between" colors right, especially if the span of the colors is
>> large.
>>
>> Jim
>>
>> On Fri, Oct 9, 2015 at 4:15 PM, Kumar Mainali <kpmainali at gmail.com> wrote:
>>
>>> Hi Jim and others:
>>>
>>> I needed color code for some color gradients in color.scale function. I
>>> found that the following translates to green to yellow to
>>> red: c(0,1,1),c(1,1,0),0. How does this string translate to the color
>>> gradient? I would like to know the gradient code for red to yellow, yellow
>>> to green and other ranges.
>>>
>>> Thanks,
>>> Kumar Mainali
>>>