Re: [R] Selecting complementary colours
Dear Thomas,
This seems simpler than the solution that I used, so I'll give it a
try.
Thanks,
John
On Tue, 22 May 2007 09:01:01 -0700 (PDT)
Thomas Lumley <[EMAIL PROTECTED]> wrote:
> On Mon, 21 May 2007, John Fox wrote:
> >
> > In retrospect, I didn't specify the problem clearly: What I want to
> be able
> > to do is to place text on a background of arbitrary (but known RGB)
> colour
> > so that the text is legible. I guess that this is better described
> as a
> > "contrasting" than a "complementary" colour.
>
> Since luminance contrasts are necessary and sufficient for readable
> text, you could use white for dark colors and black for light colors.
>
> Luminance is roughly proportional to 0.2*(R^2.4)+0.6*(G^2.4),
> suggesting something like
>
> lightdark<-function (color)
> {
> rgb <- col2rgb(color)/255
> L <- c(0.2, 0.6, 0) %*% rgb
> ifelse(L >= 0.2, "#60", "#A0")
> }
>
> This uses a pale yellow for dark backgrounds and a dark blue for
> light backgrounds, and it seems to work reasonably well.
>
> -thomas
John Fox
Department of Sociology
McMaster University
Hamilton, Ontario, Canada
http://socserv.mcmaster.ca/jfox/
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Re: [R] Selecting complementary colours
"John Fox" <[EMAIL PROTECTED]> wrote in message news:[EMAIL PROTECTED] > The object is to get contrasting colours, so that > when one is plotted over the other, the two will be readily > distinguishable. A simple approach to contrast is to compute a mean intensity by taking the mean of the three RGB components (should be 0..255) and then going with either "black" or "white" -- whichever one is "farthest" away. Look at the Color Chart with contrasting numbers http://research.stowers-institute.org/efg/R/Color/Chart/index.htm or http://research.stowers-institute.org/efg/R/Color/Chart/ColorChart.pdf efg Earl F. Glynn Stowers Institute for Medical Research __ R-help@stat.math.ethz.ch 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.
Re: [R] Selecting complementary colours
On Mon, 21 May 2007, John Fox wrote:
>
> In retrospect, I didn't specify the problem clearly: What I want to be able
> to do is to place text on a background of arbitrary (but known RGB) colour
> so that the text is legible. I guess that this is better described as a
> "contrasting" than a "complementary" colour.
Since luminance contrasts are necessary and sufficient for readable text,
you could use white for dark colors and black for light colors.
Luminance is roughly proportional to 0.2*(R^2.4)+0.6*(G^2.4), suggesting
something like
lightdark<-function (color)
{
rgb <- col2rgb(color)/255
L <- c(0.2, 0.6, 0) %*% rgb
ifelse(L >= 0.2, "#60", "#A0")
}
This uses a pale yellow for dark backgrounds and a dark blue for light
backgrounds, and it seems to work reasonably well.
-thomas
__
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Re: [R] Selecting complementary colours
Dear Chuck,
This solution works reasonably well for me. Although it occasionally
produces an error, I'm able to trap that.
Thank you -- and to everyone else who responded.
John
John Fox, Professor
Department of Sociology
McMaster University
Hamilton, Ontario
Canada L8S 4M4
905-525-9140x23604
http://socserv.mcmaster.ca/jfox
> -Original Message-
> From: Charles C. Berry [mailto:[EMAIL PROTECTED]
> Sent: Monday, May 21, 2007 8:49 PM
> To: John Fox
> Cc: 'Deepayan Sarkar'; r-help@stat.math.ethz.ch
> Subject: Re: [R] Selecting complementary colours
>
> On Mon, 21 May 2007, John Fox wrote:
>
> > Dear Deepayan,
> >
> > I actually thought of the equivalent of this approach, but
> it doesn't
> > do quite what I want.
> >
> > In retrospect, I didn't specify the problem clearly: What I
> want to be
> > able to do is to place text on a background of arbitrary (but known
> > RGB) colour so that the text is legible. I guess that this
> is better
> > described as a "contrasting" than a "complementary" colour.
>
> John,
>
> There may be no unique solution. (For gray, for example.)
>
> I am not sure (in terms of color theory) that maximizing in
> rgb space really is the right thing to do, but perhaps this
> will help you:
>
> > cval <- function(x,y) -sum((x-y)^2)
> > contrasting <- function(x)
> >
> optim(runif(3,0,255),cval,lower=0,upper=255,method="L-BFGS-B",y=x)$par
> > do.call(rgb,as.list(contrasting(col2rgb("gray"))/255))
> [1] "#00"
> > do.call(rgb,as.list(contrasting(col2rgb("gray"))/255))
> [1] "#FF"
> > do.call(rgb,as.list(contrasting(col2rgb("pink"))/255))
> [1] "#00FF00"
>
> Regards,
>
> Chuck
>
> >
>
> >
> > Your solution, for example breaks down for grays:
> >
> >> mycol <- "#88"
> >> do.call(rgb, as.list(1 - col2rgb(mycol) / 255))
> > [1] "#77"
> >
> > Thank you for the suggestion.
> >
> > John
> >
> >
> > John Fox, Professor
> > Department of Sociology
> > McMaster University
> > Hamilton, Ontario
> > Canada L8S 4M4
> > 905-525-9140x23604
> > http://socserv.mcmaster.ca/jfox
> >
> >
> >> -Original Message-
> >> From: [EMAIL PROTECTED]
> >> [mailto:[EMAIL PROTECTED] On Behalf Of Deepayan
> >> Sarkar
> >> Sent: Monday, May 21, 2007 6:45 PM
> >> To: John Fox
> >> Cc: r-help@stat.math.ethz.ch
> >> Subject: Re: [R] Selecting complementary colours
> >>
> >> On 5/21/07, John Fox <[EMAIL PROTECTED]> wrote:
> >>> Dear r-helpers,
> >>>
> >>> I wonder whether, given the "#rrggbb" representation of a colour,
> >>> there is a simple way to select the complementary colour,
> >> also expressed as a "#rrggbb"
> >>> string.
> >>>
> >>> Any suggestions would be appreciated.
> >>
> >> You want rgb2col. The following should work for any standard color
> >> specification:
> >>
> >>> mycol = "royalblue"
> >>> do.call(rgb, as.list(1 - col2rgb(mycol) / 255))
> >> [1] "#BE961E"
> >>
> >> -Deepayan
> >>
> >> __
> >> R-help@stat.math.ethz.ch 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.
> >>
> >
> > __
> > R-help@stat.math.ethz.ch 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.
> >
>
> Charles C. Berry(858) 534-2098
> Dept of
> Family/Preventive Medicine
> E mailto:[EMAIL PROTECTED] UC San Diego
> http://biostat.ucsd.edu/~cberry/ La Jolla, San Diego
> 92093-0901
>
>
>
__
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[R] Selecting complementary colours
Hi John and all, I'm getting into this late and I think that most of the bases have been touched. But just to dot some "eyes",... Some years ago, I proposed some general rules of thumb that should help in generating optimally contrasting text for nearly anyone, that have been distilled into a few simple rules at this website. http://www.lighthouse.org/accessibility/effective-color-contrast/ A basic part of the guidelines include maximizing luminance contrast. Mike Kubovy, is absolutely correct that iso- or equiluminant colors would be difficult to detect because the chromatic systems in the eye are spatially low pass, though chromatic aberration would tend to work against this for large text a little bit by adding some luminance transients at the edges. If your viewer happens to be a garden variety dichromat (protanope or deuteranope), then you have to worry about choosing colors along one of his confusion lines. For example, for a deuteranope, there exists equiluminant magenta and cyan that appear gray, so these would generate an invisible contrast for the observer (maybe some outline would be vaguely visible because of chromatic aberrations in the eye). It's a little different for the protanope because he (and it is mostly he's) has a luminosity loss, so his confusion line is not in an equiluminant plane. Early stages of some prevalent eye diseases can produce a different type of chromatic loss, in which violet vs yellow-green contrasts are difficult to detect. Colorimetrically, complementaries are defined as pairs of lights whose additive mixture matches a reference white. So, according to the definition, either gray is its own complementary, or a null light would also qualify. To arbitrarily generate true complementaries would require the lights to be specified in an additive system. So, if you wanted colorimetrically precise complementaries, you would need to have your screen/printer calibrated. HTH, Ken * Hi All, Complementary colors will not insure legibility. If the text and the background are equiluminant, visibility will be severely impaired. On May 21, 2007, at 8:22 PM, John Fox wrote: > Dear Achim, > > As I mentioned in my response to Deepayan's suggestion, I didn't > specify the > original problem clearly: The object is to get contrasting colours, > so that > when one is plotted over the other, the two will be readily > distinguishable. > Your suggestions don't do this for neutral colours: > >> x <- "#88" >> y_hcl <- as(hex2RGB(x), "polarLUV") >> y_hcl at coords[1, "H"] <- y_hcl at coords[1, "H"] + 180 >> hex(y_hcl) > [1] "#88" > >> y_hsv <- as(hex2RGB(x), "HSV") >> y_hsv at coords[1, "H"] <- y_hsv at coords[1, "H"] + 180 >> hex(y_hsv) > [1] "#88" > > Thank you for trying to help. > > John > > > John Fox, Professor > Department of Sociology > McMaster University > Hamilton, Ontario > Canada L8S 4M4 > 905-525-9140x23604 > http://socserv.mcmaster.ca/jfox > > >> -Original Message- >> From: Achim Zeileis [mailto:Achim.Zeileis at wu-wien.ac.at] >> Sent: Monday, May 21, 2007 7:07 PM >> To: John Fox >> Cc: r-help at stat.math.ethz.ch >> Subject: Re: [R] Selecting complementary colours >> >> On Mon, 21 May 2007, John Fox wrote: >> >>> Dear r-helpers, >>> >>> I wonder whether, given the "#rrggbb" representation of a colour, >>> there is a simple way to select the complementary colour, >> also expressed as a "#rrggbb" >>> string. >> >> Is the complementary color uniquely defined? My understanding >> is that you can take opposite colors on a color wheel, but >> there are of course various color wheels available. With >> "colorspace" you can experiment with this, >> e.g.: >> x <- "#81A9D0" >> y_hcl <- as(hex2RGB(x), "polarLUV") >> y_hcl at coords[1, "H"] <- y_hcl at coords[1, "H"] + 180 >> y_hcl <- hex(y_hcl) >> which is a bit more balanced than >> y_hsv <- as(hex2RGB(x), "HSV") >> y_hsv at coords[1, "H"] <- y_hsv at coords[1, "H"] + 180 >> y_hsv <- hex(y_hsv) >> >> hth, >> Z >> >> >> > > __ > R-help at stat.math.ethz.ch 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,
Re: [R] Selecting complementary colours
On Mon, 21 May 2007, John Fox wrote:
> Dear Deepayan,
>
> I actually thought of the equivalent of this approach, but it doesn't do
> quite what I want.
>
> In retrospect, I didn't specify the problem clearly: What I want to be able
> to do is to place text on a background of arbitrary (but known RGB) colour
> so that the text is legible. I guess that this is better described as a
> "contrasting" than a "complementary" colour.
John,
There may be no unique solution. (For gray, for example.)
I am not sure (in terms of color theory) that maximizing in rgb space
really is the right thing to do, but perhaps this will help you:
> cval <- function(x,y) -sum((x-y)^2)
> contrasting <- function(x)
> optim(runif(3,0,255),cval,lower=0,upper=255,method="L-BFGS-B",y=x)$par
> do.call(rgb,as.list(contrasting(col2rgb("gray"))/255))
[1] "#00"
> do.call(rgb,as.list(contrasting(col2rgb("gray"))/255))
[1] "#FF"
> do.call(rgb,as.list(contrasting(col2rgb("pink"))/255))
[1] "#00FF00"
Regards,
Chuck
>
>
> Your solution, for example breaks down for grays:
>
>> mycol <- "#88"
>> do.call(rgb, as.list(1 - col2rgb(mycol) / 255))
> [1] "#77"
>
> Thank you for the suggestion.
>
> John
>
>
> John Fox, Professor
> Department of Sociology
> McMaster University
> Hamilton, Ontario
> Canada L8S 4M4
> 905-525-9140x23604
> http://socserv.mcmaster.ca/jfox
> --------
>
>> -Original Message-
>> From: [EMAIL PROTECTED]
>> [mailto:[EMAIL PROTECTED] On Behalf Of Deepayan Sarkar
>> Sent: Monday, May 21, 2007 6:45 PM
>> To: John Fox
>> Cc: r-help@stat.math.ethz.ch
>> Subject: Re: [R] Selecting complementary colours
>>
>> On 5/21/07, John Fox <[EMAIL PROTECTED]> wrote:
>>> Dear r-helpers,
>>>
>>> I wonder whether, given the "#rrggbb" representation of a colour,
>>> there is a simple way to select the complementary colour,
>> also expressed as a "#rrggbb"
>>> string.
>>>
>>> Any suggestions would be appreciated.
>>
>> You want rgb2col. The following should work for any standard color
>> specification:
>>
>>> mycol = "royalblue"
>>> do.call(rgb, as.list(1 - col2rgb(mycol) / 255))
>> [1] "#BE961E"
>>
>> -Deepayan
>>
>> __
>> R-help@stat.math.ethz.ch 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.
>>
>
> __
> R-help@stat.math.ethz.ch 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.
>
Charles C. Berry(858) 534-2098
Dept of Family/Preventive Medicine
E mailto:[EMAIL PROTECTED] UC San Diego
http://biostat.ucsd.edu/~cberry/ La Jolla, San Diego 92093-0901
__
R-help@stat.math.ethz.ch 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.
Re: [R] Selecting complementary colours
Hi All, Complementary colors will not insure legibility. If the text and the background are equiluminant, visibility will be severely impaired. On May 21, 2007, at 8:22 PM, John Fox wrote: > Dear Achim, > > As I mentioned in my response to Deepayan's suggestion, I didn't > specify the > original problem clearly: The object is to get contrasting colours, > so that > when one is plotted over the other, the two will be readily > distinguishable. > Your suggestions don't do this for neutral colours: > >> x <- "#88" >> y_hcl <- as(hex2RGB(x), "polarLUV") >> [EMAIL PROTECTED], "H"] <- [EMAIL PROTECTED], "H"] + 180 >> hex(y_hcl) > [1] "#88" > >> y_hsv <- as(hex2RGB(x), "HSV") >> [EMAIL PROTECTED], "H"] <- [EMAIL PROTECTED], "H"] + 180 >> hex(y_hsv) > [1] "#88" > > Thank you for trying to help. > > John > > > John Fox, Professor > Department of Sociology > McMaster University > Hamilton, Ontario > Canada L8S 4M4 > 905-525-9140x23604 > http://socserv.mcmaster.ca/jfox > ---- > >> -Original Message- >> From: Achim Zeileis [mailto:[EMAIL PROTECTED] >> Sent: Monday, May 21, 2007 7:07 PM >> To: John Fox >> Cc: r-help@stat.math.ethz.ch >> Subject: Re: [R] Selecting complementary colours >> >> On Mon, 21 May 2007, John Fox wrote: >> >>> Dear r-helpers, >>> >>> I wonder whether, given the "#rrggbb" representation of a colour, >>> there is a simple way to select the complementary colour, >> also expressed as a "#rrggbb" >>> string. >> >> Is the complementary color uniquely defined? My understanding >> is that you can take opposite colors on a color wheel, but >> there are of course various color wheels available. With >> "colorspace" you can experiment with this, >> e.g.: >> x <- "#81A9D0" >> y_hcl <- as(hex2RGB(x), "polarLUV") >> [EMAIL PROTECTED], "H"] <- [EMAIL PROTECTED], "H"] + 180 >> y_hcl <- hex(y_hcl) >> which is a bit more balanced than >> y_hsv <- as(hex2RGB(x), "HSV") >> [EMAIL PROTECTED], "H"] <- [EMAIL PROTECTED], "H"] + 180 >> y_hsv <- hex(y_hsv) >> >> hth, >> Z >> >> >> > > __ > R-help@stat.math.ethz.ch 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. _ Professor Michael Kubovy University of Virginia Department of Psychology USPS: P.O.Box 400400Charlottesville, VA 22904-4400 Parcels:Room 102Gilmer Hall McCormick RoadCharlottesville, VA 22903 Office:B011+1-434-982-4729 Lab:B019+1-434-982-4751 Fax:+1-434-982-4766 WWW:http://www.people.virginia.edu/~mk9y/ __ R-help@stat.math.ethz.ch 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.
Re: [R] Selecting complementary colours
Dear Achim, As I mentioned in my response to Deepayan's suggestion, I didn't specify the original problem clearly: The object is to get contrasting colours, so that when one is plotted over the other, the two will be readily distinguishable. Your suggestions don't do this for neutral colours: > x <- "#88" > y_hcl <- as(hex2RGB(x), "polarLUV") > [EMAIL PROTECTED], "H"] <- [EMAIL PROTECTED], "H"] + 180 > hex(y_hcl) [1] "#88" > y_hsv <- as(hex2RGB(x), "HSV") > [EMAIL PROTECTED], "H"] <- [EMAIL PROTECTED], "H"] + 180 > hex(y_hsv) [1] "#88" Thank you for trying to help. John John Fox, Professor Department of Sociology McMaster University Hamilton, Ontario Canada L8S 4M4 905-525-9140x23604 http://socserv.mcmaster.ca/jfox > -Original Message- > From: Achim Zeileis [mailto:[EMAIL PROTECTED] > Sent: Monday, May 21, 2007 7:07 PM > To: John Fox > Cc: r-help@stat.math.ethz.ch > Subject: Re: [R] Selecting complementary colours > > On Mon, 21 May 2007, John Fox wrote: > > > Dear r-helpers, > > > > I wonder whether, given the "#rrggbb" representation of a colour, > > there is a simple way to select the complementary colour, > also expressed as a "#rrggbb" > > string. > > Is the complementary color uniquely defined? My understanding > is that you can take opposite colors on a color wheel, but > there are of course various color wheels available. With > "colorspace" you can experiment with this, > e.g.: > x <- "#81A9D0" > y_hcl <- as(hex2RGB(x), "polarLUV") > [EMAIL PROTECTED], "H"] <- [EMAIL PROTECTED], "H"] + 180 > y_hcl <- hex(y_hcl) > which is a bit more balanced than > y_hsv <- as(hex2RGB(x), "HSV") > [EMAIL PROTECTED], "H"] <- [EMAIL PROTECTED], "H"] + 180 > y_hsv <- hex(y_hsv) > > hth, > Z > > > __ R-help@stat.math.ethz.ch 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.
Re: [R] Selecting complementary colours
Dear Deepayan, I actually thought of the equivalent of this approach, but it doesn't do quite what I want. In retrospect, I didn't specify the problem clearly: What I want to be able to do is to place text on a background of arbitrary (but known RGB) colour so that the text is legible. I guess that this is better described as a "contrasting" than a "complementary" colour. Your solution, for example breaks down for grays: > mycol <- "#88" > do.call(rgb, as.list(1 - col2rgb(mycol) / 255)) [1] "#77" Thank you for the suggestion. John John Fox, Professor Department of Sociology McMaster University Hamilton, Ontario Canada L8S 4M4 905-525-9140x23604 http://socserv.mcmaster.ca/jfox > -Original Message- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Deepayan Sarkar > Sent: Monday, May 21, 2007 6:45 PM > To: John Fox > Cc: r-help@stat.math.ethz.ch > Subject: Re: [R] Selecting complementary colours > > On 5/21/07, John Fox <[EMAIL PROTECTED]> wrote: > > Dear r-helpers, > > > > I wonder whether, given the "#rrggbb" representation of a colour, > > there is a simple way to select the complementary colour, > also expressed as a "#rrggbb" > > string. > > > > Any suggestions would be appreciated. > > You want rgb2col. The following should work for any standard color > specification: > > > mycol = "royalblue" > > do.call(rgb, as.list(1 - col2rgb(mycol) / 255)) > [1] "#BE961E" > > -Deepayan > > __ > R-help@stat.math.ethz.ch 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. > __ R-help@stat.math.ethz.ch 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.
Re: [R] Selecting complementary colours
On Mon, 21 May 2007, John Fox wrote: > Dear r-helpers, > > I wonder whether, given the "#rrggbb" representation of a colour, there is a > simple way to select the complementary colour, also expressed as a "#rrggbb" > string. Is the complementary color uniquely defined? My understanding is that you can take opposite colors on a color wheel, but there are of course various color wheels available. With "colorspace" you can experiment with this, e.g.: x <- "#81A9D0" y_hcl <- as(hex2RGB(x), "polarLUV") [EMAIL PROTECTED], "H"] <- [EMAIL PROTECTED], "H"] + 180 y_hcl <- hex(y_hcl) which is a bit more balanced than y_hsv <- as(hex2RGB(x), "HSV") [EMAIL PROTECTED], "H"] <- [EMAIL PROTECTED], "H"] + 180 y_hsv <- hex(y_hsv) hth, Z __ R-help@stat.math.ethz.ch 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.
Re: [R] Selecting complementary colours
On 5/21/07, John Fox <[EMAIL PROTECTED]> wrote: > Dear r-helpers, > > I wonder whether, given the "#rrggbb" representation of a colour, there is a > simple way to select the complementary colour, also expressed as a "#rrggbb" > string. > > Any suggestions would be appreciated. You want rgb2col. The following should work for any standard color specification: > mycol = "royalblue" > do.call(rgb, as.list(1 - col2rgb(mycol) / 255)) [1] "#BE961E" -Deepayan __ R-help@stat.math.ethz.ch 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.
[R] Selecting complementary colours
Dear r-helpers, I wonder whether, given the "#rrggbb" representation of a colour, there is a simple way to select the complementary colour, also expressed as a "#rrggbb" string. Any suggestions would be appreciated. John John Fox, Professor Department of Sociology McMaster University Hamilton, Ontario Canada L8S 4M4 905-525-9140x23604 http://socserv.mcmaster.ca/jfox __ R-help@stat.math.ethz.ch 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.
