In fact, I erred by summing both the year and the value, so i would
recommend Peter's (much less messy) solution.
Jim
On 03/10/2014 02:57 PM, Peter Alspach wrote:
Tena koe Philip
An alternative to Jim's solution which seems to work and you may, or may not,
find less messy:
df<- read.table(text="id yr val
a 1950 1
b 1950 10
a 1951 2
b 1952 3
c 1952 4
a 1954 5
b 1954 2
c 1954 3",header=TRUE)
df1<- df[order(df$id, df$yr),]
df1$valCS<- unlist(by(df1$val, df1$id, cumsum))
df1
If you need to get back to the original order you can sort by row.names.
HTH ....
Peter Alspach
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