Understanding H and Q Searches
Pedigree Search lets you specify where in a pedigree an ancestor must appear. H and Q are how you say where.
H means half. Q means quartile. Together they let you ask a much sharper question than "does this horse appear anywhere in the pedigree".
The two halves
Every pedigree divides into two halves.
H1 is the top half, covering every ancestor on the sire side.
H2 is the bottom half, covering every ancestor on the dam side.
Searching H1 alone finds pedigrees carrying that ancestor anywhere on the sire side. Searching H2 alone does the same for the dam side.
Searching a cross
Entering one ancestor in H1 and another in H2 finds pedigrees where the first appears on the sire side and the second on the dam side.
This is the standard way to research a cross. It is asking whether two influences have worked together when they meet from opposite sides, which is the situation a mating actually creates.
Start here. A combined H1 and H2 search is the broadest useful question, and it returns enough results to tell you whether the combination is worth investigating further.
The four quartiles
Each half divides again, giving four quartiles.
- Q1 The upper quarter of the sire side, being the sire line.
- Q2 The lower quarter of the sire side.
- Q3 The upper quarter of the dam side, being the broodmare sire line.
- Q4 The lower quarter of the dam side.
Quartile searches are stricter. An ancestor that satisfies an H1 search may fail a Q1 search, because H1 accepts it anywhere on the sire side while Q1 requires it in the sire line specifically.
Why position matters
Two pedigrees can contain the same two ancestors and represent completely different genetic relationships depending on where each sits.
An ancestor in the sire line is being transmitted down the male line. The same ancestor sitting in the lower quarter of the sire side arrives through the sire's dam, which is a different route and often a different effect.
Halves tell you an influence is present on a side. Quartiles tell you how it got there.
A worked example
Enter Sadler's Wells in Q1 and Nureyev in Q3.
That search returns pedigrees where Sadler's Wells appears in the sire line and Nureyev in the broodmare sire line. It is a specific question about how those two influences perform when they arrive by those particular routes.
The same two names entered as H1 and H2 would return far more pedigrees, including many where the ancestors sit in positions you did not intend.
Which to use
Use halves when researching a cross in general, when you want volume, or when starting an investigation.
Use quartiles when position is part of your question, when a half search returns too many results to interpret, or when testing a pattern you have seen in a specific pedigree.
Working from halves to quartiles is usually the sensible order. Establish that a combination works at all, then narrow to find out where it works best.
Watch your runner counts
Every narrowing reduces the population you are measuring against. A quartile search returning a strong strike rate on a handful of runners is weaker evidence than a half search returning a moderate one on thousands.
Check the runner counts alongside any percentage. See Strike rate, and how to read it.