[R] stacked area chart

[Ista Zahn]

Hi Dimitri,
I'm not proficient with base graphics, but here is a ggplot solution:

my.data.m <- melt(my.data, id="date")
my.data.m$pn <- "+"
my.data.m[my.data.m$variable %in% c("y", "z"), "pn"] <- "-"
my.data.m$variable <- factor(my.data.m$variable, levels=c("a", "x", "y", "z"))
my.data.m$Date <- as.numeric(my.data.m$date)

ggplot(my.data.m, aes(x=Date, y=value, fill=variable)) +
  geom_area(data=subset(my.data.m, pn=="+")) +
  geom_area(data=subset(my.data.m, pn=="-")) +
  scale_x_continuous(breaks=unique(my.data.m$Date),
labels=unique(my.data.m$date)) +
  scale_fill_manual(values=c("yellow", "blue", "green", "orange")) +
  theme_bw() +
  ylab("Title of Y") +
  opts(title="Chart title", axis.text.x=theme_text(angle=70, vjust=1, hjust=1))


HTH,
Ista

On Mon, Sep 27, 2010 at 6:05 PM, Dimitri Liakhovitski
<dimitri.liakhovitski at gmail.com> wrote:
> I found a solution to my original question (see code below).
> But I have a question about cosmetics, which I always find very challenging.
> 1. How can I make all dates appear on the X axis (rotated at 90
> degrees vs. horizontal)?
> 2. How can I create vertical grid lines so that at each date there is
> a gridline?
> 3. How can I create a legend for colors, but not on top of the graph
> but on the right side, outside of the graph (because in my real data
> set I have a lot of variables - so that there'll never be enough space
> for the legend in the graph itself)
>
> Thanks a lot!
> Dimitri
>
>
> ### Creating a data set with both positives and negatives
> my.data<-data.frame(date=c(20080301,20080402,20080503,20090301,20090402,20090503,20100301,20100402,20100503),
> x=c(1.1,1.0,1.6,1,2,1.5,2.1,1.3,1.9),y=c(-4,-3,-6,-5,-7,-5.2,-6,-4,-4.9),
> z=c(-0.2,-0.3,-0.4,-0.1,-0.2,-0.05,-0.2,-0.15,-0.06),a=c(10,13,15,15,16,17,15,16,14))
> my.data$date<-as.character(my.data$date)
> my.data$date<-as.Date(my.data$date,"%Y%m%d")
> (my.data)
>
> positives<-which(colSums(my.data[2:ncol(my.data)])>0) # which vars
> have positive column sums?
> negatives<-which(colSums(my.data[2:ncol(my.data)])<0) # which vars
> have negative column sums?
>
> y.max<-1.1*max(rowSums(my.data[names(positives)])) # the max on the y
> axis of the chart
> y.min<-1.1*min(rowSums(my.data[names(negatives)])) # the min on the y
> axis of the chart
> ylim <- c(y.min, y.max)
> order.positives<-rev(rank(positives))
> order.of.pos.vars<-names(order.positives)
> order.negatives<-rev(rank(negatives))
> order.of.neg.vars<-names(order.negatives)
> order<-c(order.negatives,order.positives)
> order.of.vars<-names(order)   # the order of variables on the chart -
> from the bottom up
> ### so, the bottom-most area should be for z, the second from the
> bottom area- for y (above z)
>
> all.colors<-c('red','blue','green','orange','yellow','purple')
> xx <- c(my.data$date, rev(my.data$date))
> bottom.y.coordinates<-rowSums(my.data[names(negatives)])
>
> plot(x=my.data$date, y=bottom.y.coordinates, ylim=ylim, col='white',
> type='l', xaxt='n',
>    ylab='Title for Y', xlab='Date', main='Chart Title')
>
> for(var in order.of.neg.vars){
>        top.line.coords<-bottom.y.coordinates-my.data[[var]]
>        bottom.coords<-c(bottom.y.coordinates,rev(top.line.coords))
>        polygon(xx,bottom.coords,col=all.colors[which(names(my.data) %in% var)])
>        bottom.y.coordinates<-top.line.coords
> }
>
> for(var in order.of.pos.vars){
>        top.line.coords<-bottom.y.coordinates+my.data[[var]]
>        bottom.coords<-c(bottom.y.coordinates,rev(top.line.coords))
>        polygon(xx,bottom.coords,col=all.colors[which(names(my.data) %in% var)])
>        bottom.y.coordinates<-top.line.coords
> }
>
>
>
> On Mon, Sep 27, 2010 at 11:47 AM, Dimitri Liakhovitski
> <dimitri.liakhovitski at gmail.com> wrote:
>> Dear R-ers!
>>
>> Asking for your help with building the stacked area chart for the
>> following simple data (several variables - with date on the X axis):
>>
>> ### Creating a data set
>> my.data<-data.frame(date=c(20080301,20080402,20080503,20090301,20090402,20090503,20100301,20100402,20100503),
>> x=c(1.1,1.0,1.6,1,2,1.5,2.1,1.3,1.9),y=c(-4,-3,-6,-5,-7,-5.2,-6,-4,-4.9),
>> z=c(-0.2,-0.3,-0.4,-0.1,-0.2,-0.05,-0.2,-0.15,-0.06),a=c(4,3,5,5,6,7,5,6,4))
>> my.data$date<-as.character(my.data$date)
>> my.data$date<-as.Date(my.data$date,"%Y%m%d")
>> (my.data)
>>
>> I'd like the variables whose column values sum up to a negative number
>> to be below zero on that chart and those that add up to a positive
>> number to be above zero in the chart. I am calculating values for ylim
>> and for the order of the variable entry (bottom up) like this:
>>
>> positives<-which(colSums(my.data[2:ncol(my.data)])>0) # which vars
>> have positive column sums?
>> negatives<-which(colSums(my.data[2:ncol(my.data)])<0) # which vars
>> have negative column sums?
>>
>> y.max<-1.1*max(rowSums(my.data[names(positives)])) # the max on the y
>> axis of the chart
>> y.min<-1.1*min(rowSums(my.data[names(negatives)])) # the min on the y
>> axis of the chart
>> ylim <- c(y.min, y.max)  # ylim for the stacked area chart
>>
>> order.positives<-rev(rank(positives))
>> order.negatives<-rev(rank(negatives))
>> order<-c(order.negatives,order.positives)
>> order.of.vars<-names(order)   # the order of variables on the chart - bottom up
>> ### so, the bottom-most area should be for z, and the second from the
>> bottom area- for y (above z) - they'll be below zero
>> ### and above zero we'll have a first and x second (on top of a).
>>
>> Thanks a lot for your advice!
>>
>> --
>> Dimitri Liakhovitski
>> Ninah Consulting
>> www.ninah.com
>>
>
>
>
> --
> Dimitri Liakhovitski
> Ninah Consulting
> www.ninah.com
>
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> and provide commented, minimal, self-contained, reproducible code.
>



-- 
Ista Zahn
Graduate student
University of Rochester
Department of Clinical and Social Psychology
http://yourpsyche.org