[R] data management question

[Berend Hasselman]

On 08-02-2012, at 06:23, Sebastián Daza wrote:

> Hi everyone,
> I would like to have a function to compute some values in a dataset.
> First, I have to define a value for the lx variable in row 1 (e.g.,
> 100,000), npx is a given proportion. lx of row 2 is equal to lx of row
> 1 times npx of row 1. I can do this row by row...
> 
> data[1,"lx"]  <- 100000
> data[2,"lx"]  <- data[1,"lx"]*data[1,"npx"]
> data[3,"lx"]  <- data[2,"lx"]*data[2,"npx"]
> data[4,"lx"]  <- data[3,"lx"]*data[3,"npx"]
> ...
> data[19,"lx"]  <- data[18,"lx"]*data[18,"npx"]
> 
> Any ideas about how to define this in a function or in a more systematic way?

Something like

data[,"lx"] <- 100000 * c(1, cumprod(data[,"npx"]))

In ypur example column "lx" has length 19 and column "npx" appears to have length 18.
So you may have to adjust lengths.

Berend