[R] Color US counties on US map using a numeric variable for color intensity

Adams, Jean jvadams at usgs.gov
Fri Apr 3 19:41:17 CEST 2015 

Dimitri,

To answer your questions:
The colorRamp() function creates a new function, newpal().
The value returned by newpal() is a numeric matrix of RGB color values.
The rgb() function is then used to convert this numeric matrix to colors,
with the argument maxColorValue
giving the maximum of the color values range.  Typically either 255 or 1.
See the help files for more information

?colorRamp
?rgb


I think Jim Lemon's suggestion to use color.scale() function is a handier
solution.

Jean

On Thu, Apr 2, 2015 at 6:05 PM, Dimitri Liakhovitski <
dimitri.liakhovitski at gmail.com> wrote:

> This is really cool, Jim - thanks a lot!
>
> On Thu, Apr 2, 2015 at 6:18 PM, Jim Lemon <drjimlemon at gmail.com> wrote:
> > Hi Dimitri,
> > You can also try the color.scale function in plotrix, which allows you to
> > specify the NA color in the call.
> >
> >
> newcol<-color.scale(mydata.final$Mean.Wait,extremes=c("yellow","red"),na.color="white")
> >
> > Jim
> >
> >
> > On Fri, Apr 3, 2015 at 8:08 AM, Dimitri Liakhovitski
> > <dimitri.liakhovitski at gmail.com> wrote:
> >>
> >> Jean, I think I fixed it:
> >>
> >> newpal <- colorRamp(c("yellow", "red"))
> >> missing <- is.na(mydata.final$Mean.Wait)
> >> newcol <- ifelse(missing, "white",
> >>
> >> rgb(newpal(mydata.final$Mean.Wait[!is.na(mydata.final$Mean.Wait)]/
> >>                                   max(mydata.final$Mean.Wait,
> >> na.rm=T)), maxColorValue=255))
> >> map('county', fill=TRUE, col=newcol,
> >>     resolution=0, lty=0, bg="transparent")
> >> map('state', lwd=1, add=TRUE)
> >>
> >> One understanding question: what exactly does this rgb line do and why
> >> do we have to say "maxColorValue=255"?
> >> Thank you!
> >>
> >> On Thu, Apr 2, 2015 at 5:02 PM, Dimitri Liakhovitski
> >> <dimitri.liakhovitski at gmail.com> wrote:
> >> > Thank you, Jean, but I think this newcol line is not working. I am
> >> > running:
> >> >
> >> > newcol <- ifelse(missing, "white",
> >> >
> >> > rgb(newpal(mydata.final$Mean.Wait/max(mydata.final$Mean.Wait,
> >> > na.rm=T)),
> >> >                      maxColorValue=255))
> >> >
> >> > # And I am getting:
> >> > Error in rgb(newpal(mydata.final$Mean.Wait/max(mydata.final$Mean.Wait,
> >> > :
> >> >   color intensity NA, not in 0:255
> >> >
> >> > I think it's not liking the NAs - despite the ifelse...
> >> >
> >> > On Thu, Apr 2, 2015 at 4:26 PM, Adams, Jean <jvadams at usgs.gov> wrote:
> >> >> Dimitri,
> >> >>
> >> >> You could use colorRamp() and rgb() to get more continuous colors.
> >> >> For example
> >> >>
> >> >> newpal <- colorRamp(c("yellow", "red"))
> >> >> missing <- is.na(mydata.final$Mean.Wait)
> >> >> newcol <- ifelse(missing, "white",
> >> >>   rgb(newpal(mydat$Mean.Wait/max(mydat$Mean.Wait)),
> maxColorValue=255))
> >> >> map('county', fill=TRUE, col=newcol,
> >> >>             resolution=0, lty=0, bg="transparent")
> >> >> map('state', lwd=1, add=TRUE)
> >> >>
> >> >> Jean
> >> >>
> >> >>
> >> >> On Thu, Apr 2, 2015 at 12:03 PM, Dimitri Liakhovitski
> >> >> <dimitri.liakhovitski at gmail.com> wrote:
> >> >>>
> >> >>> I have a data frame 'mydata.final' (see below) that contains US
> >> >>> counties and a continuous numeric variable 'Mean.Wait' that ranges
> >> >>> from zero to 10 or so. I also created variable 'wait' that is based
> on
> >> >>> the 'Mean.Wait' and takes on discrete values from 1 (lowest values
> on
> >> >>> 'Mean.Wait') to 5 (highest values on 'Mean.Wait').
> >> >>>
> >> >>> I can create a map of the US with the counties colored based on the
> >> >>> values of 'wait' using R package 'maps':
> >> >>>
> >> >>> #################################################################
> >> >>> ### Generating an artificial data file:
> >> >>> #################################################################
> >> >>> library(maps)
> >> >>> mydata.final <- data.frame(county = (map('county', plot =
> >> >>> FALSE)$names),
> >> >>>                  stringsAsFactors = F)
> >> >>>
> >> >>> ### My numeric variable:
> >> >>> set.seed(123)
> >> >>> mydata.final$Mean.Wait <- runif(nrow(mydata.final)) * 10
> >> >>>
> >> >>> ### Introducing NAs to mimic my real data set:
> >> >>> set.seed(1234)
> >> >>> mydata.final$Mean.Wait[sample(1:nrow(mydata.final), 1500)] <- NA
> >> >>>
> >> >>> ### Cutting the original numeric variable into categories
> >> >>> ### because I don't know how to color based on 'Mean.Wait':
> >> >>> mydata.final$wait <- cut(mydata.final$Mean.Wait, breaks = 5)
> >> >>> levels(mydata.final$wait) <- 1:5
> >> >>> mydata.final$wait <- as.numeric(as.character(mydata.final$wait))
> >> >>>
> >> >>> ####################################################################
> >> >>> Building a US map based on 'wait' (5 categories)
> >> >>> #################################################################
> >> >>>
> >> >>> ### Creating my 5 colors:
> >> >>> pal <- colorRampPalette(c("yellow", "red"))
> >> >>> allcolors <- pal(5)
> >> >>>
> >> >>> ### Looking at my 5 colors:
> >> >>> barplot(1:5, rep(1,5), col = allcolors, horiz = T)
> >> >>>
> >> >>> ### Builiding the US map using 5 categories in 'wait':
> >> >>> map('county', fill = TRUE, col = allcolors[mydata.final$wait],
> >> >>>             resolution = 0, lty = 0, bg = "transparent")
> >> >>> map('state', lwd=1, add=TRUE)
> >> >>>
> >> >>> My goal is: instead of splitting 'Mean.Wait' into 5 ordered
> categories
> >> >>> ('wait'), I'd like to color the counties on the map based on the
> >> >>> intensity of my (continuous) 'Mean.Wait'. What would be the way to
> do
> >> >>> it and maybe even to add a legend?
> >> >>> Thanks a lot!
> >> >>>
> >> >>> --
> >> >>> Dimitri Liakhovitski
> >> >>>
> >> >>> ______________________________________________
> >> >>> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> >> >>> 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.
> >> >>
> >> >>
> >> >
> >> >
> >> >
> >> > --
> >> > Dimitri Liakhovitski
> >>
> >>
> >>
> >> --
> >> Dimitri Liakhovitski
> >>
> >> ______________________________________________
> >> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> >> 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.
> >
> >
>
>
>
> --
> Dimitri Liakhovitski
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> 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.
>

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