R help - Mar 2011 - Help with plotting a line that is multicoloured based on levels of a factor

Hi All, 

 

I'm trying to plot data that is a time series of flows that are associated
with a specific level, and I would like each level to represent a colour
in a line plot.  Here is some data that approximates what I'm using:

 

date=c(1:300)

flow=sin(2*pi/53*c(1:300))

levels=c(rep(c("high","med","low"),100))

data=cbind.data.frame(date, flow, levels)

 

the "levels" column represents the levels of flow.  What I've done
so far
is to plot this data using coloured points corresponding with each flow
level:

 

colour=ifelse(data$levels=="high","red",

                ifelse(data$levels=="med","green",

               
ifelse(data$levels=="low","blue","")))

plot(date, flow, col=colour)

 

What I would like to do instead is to plot the line of this data, not the
points.  i.e., 

plot(date, flow, type="l")

 

But I would like the colour of the line to change with each level, i.e.,

plot(date, flow, type="l", col=colour)

 

But this doesn't work because the line is continuous and the colours are
discrete.  I looked into using clipplot, but I'm not sure how I would
specify limits that would give different sections of the line correct
colours.  Does anyone know of a way to draw a line with different colours?
One way I thought of was to plot each level of flow separately and then
build the plot up, i.e., 

plot(data$date[data$levels=="high"],
data$flow[data$levels=="high"],
col="red", type="l")

lines(data$date[data$levels=="med"],
data$flow[data$levels=="med"],
col="green", type="l")

lines(data$date[data$levels=="low"],
data$flow[data$levels=="low"],
col="blue", type="l")

 

But the line fills in data gaps, so this doesn't work.

 

Any help would be much appreciated!  Thank you.

 

-Pam Allen

pallen at hatfieldgroup.com

Hi!


Not an elegant solution, but seems to work:

date <- c(1:300)
flow <- sin(2*pi/53*c(1:300))
levels <-
factor(rep(c("high","med","low"),100))
data <- cbind.data.frame(date, flow, levels)
colours <- as.numeric(levels)+1

# interpolate
resolution <- 0.001
appres <- approx(date,flow,seq(min(date),max(date),resolution))
appres.colour <- rep(colours,each=1/resolution)[1:length(appres[[1]])]

# plot
plot(appres,col=appres.colour,pch=16,cex=0.5)

Of course you should play with the resolution, pch and cex parameters to
get a higher quality plot, or might use other function for interpolation.


Regards,
  Denes



>
>
>
>
> Hi All,
>
>
>
> I'm trying to plot data that is a time series of flows that are
associated
> with a specific level, and I would like each level to represent a colour
> in a line plot.  Here is some data that approximates what I'm using:
>
>
>
> date=c(1:300)
>
> flow=sin(2*pi/53*c(1:300))
>
> levels=c(rep(c("high","med","low"),100))
>
> data=cbind.data.frame(date, flow, levels)
>
>
>
> the "levels" column represents the levels of flow.  What I've
done so far
> is to plot this data using coloured points corresponding with each flow
> level:
>
>
>
> colour=ifelse(data$levels=="high","red",
>
>                 ifelse(data$levels=="med","green",
>
>                
ifelse(data$levels=="low","blue","")))
>
> plot(date, flow, col=colour)
>
>
>
> What I would like to do instead is to plot the line of this data, not the
> points.  i.e.,
>
> plot(date, flow, type="l")
>
>
>
> But I would like the colour of the line to change with each level, i.e.,
>
> plot(date, flow, type="l", col=colour)
>
>
>
> But this doesn't work because the line is continuous and the colours
are
> discrete.  I looked into using clipplot, but I'm not sure how I would
> specify limits that would give different sections of the line correct
> colours.  Does anyone know of a way to draw a line with different colours?
> One way I thought of was to plot each level of flow separately and then
> build the plot up, i.e.,
>
> plot(data$date[data$levels=="high"],
data$flow[data$levels=="high"],
> col="red", type="l")
>
> lines(data$date[data$levels=="med"],
data$flow[data$levels=="med"],
> col="green", type="l")
>
> lines(data$date[data$levels=="low"],
data$flow[data$levels=="low"],
> col="blue", type="l")
>
>
>
> But the line fills in data gaps, so this doesn't work.
>
>
>
> Any help would be much appreciated!  Thank you.
>
>
>
> -Pam Allen
>
> pallen at hatfieldgroup.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.
>

Hi,

because each colour is defined on non-consecutive points, you'll
probably need to cut the intervals to define segments around each
point. One approach might be the following,

d = transform(data,  start = date - c(0, diff(date)/2), end = date +
c(0, diff(date)/2) )
d$start.y = approx(d$date, d$flow, d$start)$y
d$end.y = approx(d$date, d$flow, d$end)$y
library(ggplot2)
ggplot(d) + geom_segment(aes(x=start,y=start.y, xend=end, yend=end.y,
colour=levels))

HTH,

baptiste

On 18 March 2011 11:33, Pamela Allen <pallen at hatfieldgroup.com>
wrote:
>
>
>
>
> Hi All,
>
>
>
> I'm trying to plot data that is a time series of flows that are
associated
> with a specific level, and I would like each level to represent a colour
> in a line plot. ?Here is some data that approximates what I'm using:
>
>
>
> date=c(1:300)
>
> flow=sin(2*pi/53*c(1:300))
>
> levels=c(rep(c("high","med","low"),100))
>
> data=cbind.data.frame(date, flow, levels)
>
>
>
> the "levels" column represents the levels of flow. ?What I've
done so far
> is to plot this data using coloured points corresponding with each flow
> level:
>
>
>
> colour=ifelse(data$levels=="high","red",
>
> ? ? ? ? ? ? ? ?ifelse(data$levels=="med","green",
>
> ? ? ? ? ? ? ?
?ifelse(data$levels=="low","blue","")))
>
> plot(date, flow, col=colour)
>
>
>
> What I would like to do instead is to plot the line of this data, not the
> points. ?i.e.,
>
> plot(date, flow, type="l")
>
>
>
> But I would like the colour of the line to change with each level, i.e.,
>
> plot(date, flow, type="l", col=colour)
>
>
>
> But this doesn't work because the line is continuous and the colours
are
> discrete. ?I looked into using clipplot, but I'm not sure how I would
> specify limits that would give different sections of the line correct
> colours. ?Does anyone know of a way to draw a line with different colours?
> One way I thought of was to plot each level of flow separately and then
> build the plot up, i.e.,
>
> plot(data$date[data$levels=="high"],
data$flow[data$levels=="high"],
> col="red", type="l")
>
> lines(data$date[data$levels=="med"],
data$flow[data$levels=="med"],
> col="green", type="l")
>
> lines(data$date[data$levels=="low"],
data$flow[data$levels=="low"],
> col="blue", type="l")
>
>
>
> But the line fills in data gaps, so this doesn't work.
>
>
>
> Any help would be much appreciated! ?Thank you.
>
>
>
> -Pam Allen
>
> pallen at hatfieldgroup.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.
>
>

On Mar 17, 2011, at 6:33 PM, Pamela Allen wrote:
>
> Hi All,
> I'm trying to plot data that is a time series of flows that are  
> associated
> with a specific level, and I would like each level to represent a  
> colour
> in a line plot.  Here is some data that approximates what I'm using:
>
> date=c(1:300)
> flow=sin(2*pi/53*c(1:300))
> levels=c(rep(c("high","med","low"),100))
> data=cbind.data.frame(date, flow, levels)
>
> the "levels" column represents the levels of flow.  What I've
done
> so far
> is to plot this data using coloured points corresponding with each  
> flow
> level:
>
> colour=ifelse(data$levels=="high","red",
>                ifelse(data$levels=="med","green",
>               
ifelse(data$levels=="low","blue","")))
> plot(date, flow, col=colour)
>
> What I would like to do instead is to plot the line of this data,  
> not the
> points.  i.e.,
>
> plot(date, flow, type="l")
>
> But I would like the colour of the line to change with each level,  
> i.e.,
>
> plot(date, flow, type="l", col=colour)
>
> But this doesn't work because the line is continuous and the colours  
> are
> discrete.  I looked into using clipplot, but I'm not sure how I would
> specify limits that would give different sections of the line correct
> colours.  Does anyone know of a way to draw a line with different  
> colours?
> One way I thought of was to plot each level of flow separately and  
> then
> build the plot up, i.e.,
>
> plot(data$date[data$levels=="high"],
data$flow[data$levels=="high"],
> col="red", type="l")
>
> lines(data$date[data$levels=="med"],
data$flow[data$levels=="med"],
> col="green", type="l")
>
> lines(data$date[data$levels=="low"],
data$flow[data$levels=="low"],
> col="blue", type="l")
>
>
>
> But the line fills in data gaps, so this doesn't work.
I haven't worked through what you have done but it sounds as though  
you want this function from the plotrix package;

color.scale.lines	# Display line segments with scaled
colors
>
>
>
> Any help would be much appreciated!  Thank you.
>
> -Pam Allen
>
> pallen at hatfieldgroup.com
> .
David Winsemius, MD
West Hartford, CT

Hello again, 

I wrote an example that better represents my data, since the coloured points
are actually consecutive, but with variable lengths:

date=as.Date(c(1:300))
flow=sin(2*pi/53*c(1:300))
levels=c(rep(c("high","med","low"),100))
data=cbind.data.frame(date, flow, levels)

library(zoo)
z <- zoo(data$flow, data$date)
zz=cbind.data.frame(date=as.Date(rownames(cbind.data.frame(rollapply(z, 2,
align = "right", FUN="+")))),flow.change=(rollapply(z, 2,
align "right",FUN="+" )))
names(zz)=c("date","todays.flow","next.day.flow")
zzz=cbind.data.frame(zz[,1], (zz[,3]-zz[,2]))
names(zzz)=c("date","change.flow") 
data2=merge(data, zzz)
rate=zoo(data2$change.flow,data2$date)
x=cbind.data.frame(date=as.Date(rownames(cbind.data.frame(rollapply(rate, 2,
align="left", FUN="+")))), sign=rollapply(rate, 2,
align="left",FUN="+"))
names(x)=c("date","todays.change","next.day.change")
xx=cbind.data.frame(x[,1],(x[,3]*x[,2]))
names(xx)=c("date","sign") 
data2=merge(data2, xx)

data3=cbind(data2,pass1	ifelse(data2$flow<0, "extreme.low",
	ifelse(data2$flow>=0.9, "extreme.high","NA")))  
data4=cbind(data3, pass2
ifelse(data3$flow<0.8&data3$flow>0&data3$change.flow>=0&data3$change>=0&data3$pass1=="NA","medium"
, 

ifelse(data3$flow<0.7&data3$flow>0&data3$change.flow<0&data3$change<0&data3$pass1=="NA","medium","NA")))
data4$pass1=paste(data4$pass1, data4$pass2)
data4$pass1=replace(data4$pass1, data4$pass1=="NA NA",
"low")

dat=cbind(data4[,1:5], class	ifelse(data4$pass1=="extreme.high
NA","1.Extreme.High",
	ifelse(data4$pass1=="NA medium","2.Medium",
	ifelse(data4$pass1=="low","3.Low",
	ifelse(data4$pass1=="extreme.low
NA","4.Extreme.Low",NA)))))

colour=ifelse(dat$class=="1.Extreme.High","red",
               ifelse(dat$class=="2.Medium","green",
               ifelse(dat$class=="3.Low","blue",
	
ifelse(dat$class=="4.Extreme.Low","purple",""))))
plot(dat$date, dat$flow, col=colour) 


What I would like to do is to plot this using a line with the correct
colours instead of points, i.e.:

plot(dat$date, dat$flow, col=colour, type="l") ##Doesn't work,
because the
line is continuous

Any help would be much appreciated.  Thank you!

-Pam 

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