How many people made it from the first step to the last, and where the rest stopped.

Nothing else on Hex does this. Plausible Community Edition withholds funnels as a paid feature, so in Elixir today the only way to answer this question is to ship your data to PostHog.

Pixelex.Query.Funnel.run("shop", range, [
  "px.pageview", "view_doctor", "book_click", "booking_completed"
])

%{
  steps: [
    %{name: "px.pageview",        count: 4182, rate: 1.0,    step_rate: 1.0,   dropped: 3011},
    %{name: "view_doctor",        count: 1171, rate: 0.28,   step_rate: 0.28,  dropped: 894},
    %{name: "book_click",         count: 277,  rate: 0.066,  step_rate: 0.237, dropped: 129},
    %{name: "booking_completed",  count: 148,  rate: 0.035,  step_rate: 0.534, dropped: 0}
  ],
  conversion_rate: 0.035,
  subject: :visitor
}

rate is against the first step; step_rate is against the step before — the second is what tells you which step is broken.

Order is enforced, not assumed

Each step is built from the one before it in its own CTE, so step 3 only counts events that happened at or after that subject's step 2. The shortcut most implementations take — min(occurred_at) FILTER (WHERE name = step_n) in a single pass — silently drops anyone who did step 3 before step 2 and again after it, and silently counts nobody whose steps interleave. This costs one CTE per step and is correct.

Which subject: :visitor or :user

visitor_id is a hash under a salt that rotates every UTC day, so a funnel keyed on it cannot span midnight. That is right for a checkout and wrong for an onboarding funnel measured over a week.

run(site, range, steps, subject: :user)

keys on user_id instead, which only exists after Pixelex.identify/3. Pick :visitor for a single-visit funnel and :user for anything longer, and be aware that :user counts only signed-in people.

Conversion window

run(site, range, steps, within: {2, "hours"})

bounds how long a subject has to get from one step to the next. Without it, a visitor who bounced in March and converted in May counts as one funnel.