[R] beginner programming question

[Ray Brownrigg]

> From: "Gabor Grothendieck" <ggrothendieck at myway.com>
> Date: Wed, 17 Dec 2003 15:02:49 -0500 (EST)
> 
> Define function f to take a vector as input representing
> a single input row.   f should (1) transform this to a vector 
> representing the required row of output or else (2) produce 
> NULL if no row is to be output for that input row.
> 
> Then use this code where z is your input matrix:
> 
> t( matrix( unlist( apply( z, 1, f ) ), 2) )
> 
But as has been pointed out recently, apply really is still just a for
loop.

> > From: Adrian Dusa <adi at roda.ro>
> > Date: Wed, 17 Dec 2003 21:28:05 +0200 
> > 
> > I have a (rather theoretical) programming problem for which I have found
> > a solution, but I feel it is a rather poor one. I wonder if there's some
> > other (more clever) solution, using (maybe?) vectorization or
> > subscripting.

Here is a subscripting solution, where (for consistency with above) z is
your data [from read.table(filename, header=T)]:

> z
  rel1 rel2 rel3 age0 age1 age2 age3 sex0 sex1 sex2 sex3
1    1    3   NA   25   23    2   NA    1    2    1   NA
2    4    1    3   35   67   34   10    2    2    1    2
3    1    4    4   39   40   59   60    1    2    2    1
4    4   NA   NA   45   70   NA   NA    2    2   NA   NA
> res <- matrix(NA, nrow=length(z[, 1]), ncol=2,
         dimnames=list(rownames=rownames(z), colnames=c("ageh", "agew")))
> w <- w0 <- w1 <- w2 <- which(z[, c("rel1", "rel2", "rel3")] == 1, T)
					# find spouse entries
> w0[, 2] <- z[, "sex0"][w[, 1]]	# indices for respondent's age
> w1[, 2] <- 3 - w0[, 2]		# indices for spouse's age
> w2[, 2] <- 4 + w[, 2]			# indices of spouse's age
> res[w0] <- z[, "age0"][w[, 1]]	# set respondent's age
> res[w1] <- z[w2]			# set spouse's age
> res
        colnames
rownames ageh agew
       1   25   23
       2   34   35
       3   39   40
       4   NA   NA
>
Ray Brownrigg