[R] Computing growth rate

[Berend Hasselman]

> On 15 Dec 2016, at 13:34, Brijesh Mishra <brijeshkmishra at gmail.com> wrote:
> 
> Dear Mr Hasselman,
> 
> I missed you mail, while I was typing my own mail as a reply to Mr.
> Barradas suggestion. In fact, I implemented your suggestion even
> before reading it. But, I have a concern that I have noted (though its
> only hypothetical- such a scenario is very unlikely to occur). Is
> there a way to restrict such calculations co_code1 wise?

Like this?

df2 <- ddply(df1,"co_code1", transform,
    growth=c(NA, ifelse(diff(fyear1)==1, (exp(diff(log(sales1)))-1)*100,NA))
    )


But do also look at Petr Pikal's solution. Which of the two solutions you prefer depends on what you want in your special case.

Berend