[R] A basic design question for R

[Rui Barradas]

Hello,

Follow this example. It uses a list to hold the mortality curves.
Since there are only two different gender/age combinations, it first 
gets all such unique combinations and then creates a list of the 
appropriate length. Then assigns a matrix to the first list element.

DF <- read.table(text="
Gender  Age
  M          70
  F           65
  M          70
", header=TRUE)

# get unique gender&age
nms <- unique(apply(DF, 1, paste, collapse="."))
n <- length(nms)

# Create a list:
#   list are meant to hold any type of related objects
mort.curve <- vector("list", n)
names(mort.curve) <- nms

# Assign a value to its 1st element
mort.curve[[ 1 ]] <- matrix(1:12, nrow=4)
mort.curve$M.70  # see it
mort.curve[[ "M.70" ]]  # the same
mort.curve[[ nms[1] ]]  # the same


Alternatively, if you want each data.frame row to correspond to its own 
list element, the list would be vector("list", nrow(DF)). Anyway, list 
are very flexible, and the premier choice for that sort of problem.

Hope this helps,

Rui Barradas

Em 16-06-2012 16:50, Onur Uncu escreveu:
> Hello R Community,
>
> I have the following design question. I have a data set that looks
> like this (shortened for the sake of example).
>
> Gender  Age
>   M          70
>   F           65
>   M          70
>
> Each row represents a person with an age/gender combination. We could
> put this data into a data frame.
>
> Now, I would like to do some actuarial analysis on this data set. To
> do so, I need to create and store a mortality curve for each person in
> the table (a mortality curve is a matrix with 2 columns: date and
> survival probability). I can write a function that returns a mortality
> curve given gender and age.  The question is the following: In what
> data format should I store all these mortality curve objects? Should I
> add a column to the data frame and each entry in that column is a
> matrix (a mortality curve)? This way, the mortality curve would be
> stored next to age/gender data in the data frame. However, I read in
> several places that putting vectors/matrices as elements of a data
> frame is a bad idea. I do not know why. What is a good design choice
> in this instance please? How should I store the mortality curves?
>
> Thank you for your help.
>
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