Thank you very much. As for the second part, for every price change, the
percentage of every price change can be calculated (i.e. amount of
change divided by previous price). I was looking for a way to merely
find the mean and median of all price change percentages for each
country. I don't know if that's helpful or not. But thats very much for
the first part, thats the harder part for me I think.
Jia Ying Mei
Jim Lemon wrote:
On Tue, 2008-07-22 at 16:31 -0400, Jia Ying Mei wrote:
Hi everyone,
I am not new to R, but its been over a year since I've used it, so I
don't remember how to do some things.
I have a data set (in excel currently, but will be converted to text),
that has date, country and price, with a price for every country for
every date. I need to find the mean and median of the interval between
price changes for each country and the mean and median percentage change
for each price change within the data for a single country.
How should I go about doing this? I'd appreciate any help.
Hi Jia,
I'm not too sure what you mean by the second set of means and medians,
but this should get you started:
# first make up some data
jym.df<-data.frame(country=rep(c("au","br""cn","in","us"),each=100),
date=rep(as.Date("02/02/2008",
format="%d/%m/%Y"),500)+sample(-40:40,500,TRUE),
price=rnorm(500,100,20))
# get the intervals by country - have to create a new data frame
jymint.df<-data.frame(country=rep(levels(jym.df$country),each=99),
intervals=unlist(tapply(jym.df$date,jym.df$country,diff)))
library(prettyR)
# break down the intervals by country
brkdn(intervals~country,jymint.df,num.desc=c("mean","median"))
Jim
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