Pedigree / Identifying Immediate Family of Index Animal

[Ben Bimber]

I have a data frame containing the Id, Mother, Father and Sex from about 10,000 animals in our colony.  I am interested in graphing simple family trees for a given subject or small number of subjects.  The basic idea is: start with data frame from entire colony and list of index animals.  I need to identify all immediate relatives of these index animals and plot the pedigree for them.  We're not trying to do any sort of real analysis, just present a visualization of the family structure.  I have used the kinship and pedigree packages to plot the pedigree.  My question relates to efficiently identifying the animals to include in the pedigree:

Starting with the data frame of ~10,000 records, I want to use a set of index animals to extract the immediate relatives and plot only a small number in the pedigree.  'Immediate relatives' is somewhat of an ambiguous term - I am currently defining it as 3 generations forward and 3 backward.  Currently, I have a somewhat ugly approach where I recursively calculate each generation forward or backward and build a new dataframe.  Is there a better approach or package that does this?  I realize my code should be written better to get rid of the loops, so if anyone has suggestions there I would appreciate this as well.  Thanks in advance.

Code to calculate generations forward and backward:

#queryIds holds the unique Ids for parents of the index animals
queryIds = unique(c(ped$Sire, ped$Dam));
for(i in 1:gens){
    if (length(queryIds) == 0){break};

    #allPed is the dataframe with Id,Dam,Sire and Sex for animals in our colony
    newRows <- subset(allPed, Id %in% queryIds);
    queryIds = c(newRows$Sire, newRows$Dam);
    ped <- unique(rbind(newRows,ped));
}


#build forwards
#when calculating children, queryIds holds the Ids of the previous generation
queryIds = unique(ped$Id);
for(i in 1:gens){
    if (length(queryIds)==0){break};

    #allPed is the dataframe with Id,Dam,Sire and Sex for animals in our colony
    newRows <- subset(allPed, Sire %in% queryIds | Dam %in% queryIds);
    queryIds = newRows$Id;
    ped <- unique(rbind(newRows,ped));
}