[R] Developing functions

[daniel@sintesys.com.ar]

Hi,
I´m new in R. I´m working with similarity coefficients for clustering
items. I created one function (coef), to calculate the coefficients from
two pairs of vectors and then, as an example, the function
simple_matching,
taking a data.frame(X) and using coef in a for cicle.
It works, but I believe it is a bad way to do so (I believe the for cicle
is not necessary). Somebody can suggest anything better.
Thanks
Daniel Rozengardt

coef<-function(x1,x2){a<-sum(ifelse(x1==1&x2==1,1,0));
b<-sum(ifelse(x1==1&x2==0,1,0));
c<-sum(ifelse(x1==0&x2==1,1,0));
d<-sum(ifelse(x1==0&x2==0,1,0));
ret<-cbind(a,b,c,d);
ret
}

simple_matching<-function(X) {
ret<-matrix(ncol=dim(X)[1],nrow=dim(X)[1]);
diag(ret)<-1;
for (i in 2:length(X[,1])) {
	for (j in i:length(X[,1])) {
	vec<-coef(X[i-1,],X[j,]);
	result<-(vec[1]+vec[3])/sum(vec);
	ret[i-1,j]<-result;
	ret[j,i-1]<-result}};
ret}