On 06/29/2010 01:04 AM, Simon Kiss wrote:
Dear colleagues,
I have extracted the dates of several news stories from a newspaper data
base to chart coverage trends of an issue over time. They are in a data
frame that looks just like one generated by the reproducible code below.
I can already generate a histogram of the dates with various intervals
(months, quarters, weeks years) using hist.Date. However, there are two
other things I'd like to do.
First, I'd like to either create a stacked histogram so that one could
see whether one newspaper really pushed coverage of an issue at a
certain point while others then followed later on in time. Second, or
alternatively, I would like to do a line graph of the same data for the
different papers to represent the same trends.
I guess what I'm finding challenging is that I don't have counts of the
number of stories on each day or in each week or in each month; I just
have the dates themselves. The date.Hist command was very useful in
turning those into bins, but I'd like to push it a bit further and to a
stacked histogram or a multiple line chart.
Can anyone suggest a way to go about doing this?
I should say, I played around in Hadley Wickham's ggplot package and
looked at his website, and there is a way to render multiple lines here:
http://had.co.nz/ggplot2/scale_date.html
but it was not clear to me how to plot just the dates or an index of the
dates as I don't have a value for the y axis, other than the number of
times a story was published in that time frame.
Hi Simon,
I had to think about this for a while, but the following may be what you
want. It also gave me an idea for a new plot. Thanks.
Jim
library(plotrix)
count1<-
hist(as.numeric(test_df$test2[test_df$test=="Globe and Mail"]),
breaks=6)$counts
count2<-
hist(as.numeric(test_df$test2[test_df$test=="Post"]),
breaks=6)$counts
count3<-
hist(as.numeric(test_df$test2[test_df$test=="Star"]),
breaks=6)$counts
plot(test_df$test2,test_df$test,ylim=c(0.4,3.6),type="n",
main="Date of articles",xlab="Year",ylab="Journal",axes=FALSE)
yearpos<-seq(12599,14425,length.out=6)
axis(1,at=yearpos,labels=2004:2009)
axis(2,at=1:3,labels=c("Globe and Mail","Post","Star"))
box()
dispersion(yearpos,rep(1,6),count1/(max(count1)*2),
type="l",fill="green")
dispersion(yearpos,rep(2,6),count2/(max(count2)*2),
type="l",fill="red")
dispersion(yearpos[1:5],rep(3,5),count3/(max(count3)*2),
type="l",fill="blue")
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