R.QF Function (Gnumeric)

• Introduced: First release not established; named in Gnumeric 1.5.1 release notes.
• Supported in: Gnumeric 1.12.62; no retirement is established.
• Scope: Desktop Gnumeric with its Statistical Functions From R plugin. English comma-separated formulas are shown.
• Checked: October 14, 2026. Tables and the named advanced check use 1.12.57 ssconvert. Current 1.12.62 source was inspected; that release was not executed.

R.QF inverts the central F distribution. Its default probability is the lower cumulative probability, whereas lower_tail FALSE interprets the input as an upper-tail probability. Versioned function help.

=R.QF(probability,numerator_df,denominator_df[,lower_tail[,log_p]])

• probability: an ordinary probability from 0 through 1, or its natural log when requested.
• numerator_df, denominator_df: positive real degrees, preserving their order.
• lower_tail: optional TRUE for the lower cumulative probability; FALSE requests the upper tail.
• log_p: optional FALSE. TRUE uses natural-log probabilities, not base-10 logarithms.

Brackets mark optional arguments; do not type them. Current worksheet implementation.

These self-contained formulas were recalculated natively. Ordinary-domain results were checked against independent mathematics; source guards explain the boundary cases. Results are rounded to twelve decimal places, or thirteen significant digits for small nonzero values. This is presentation precision, not a universal accuracy guarantee.

For numerator degree 5 and denominator degree 10, lower probability 0.95 gives 3.325834530413. Upper probability 0.05 gives the same cutoff. Supplying 0.05 in the default lower-tail mode would select the lower critical value instead.

With degrees 2 and 2, the inverse has the simple form p/(1−p): probabilities 0.25, 0.5 and 0.75 give 1/3, 1 and 3. These closed forms provide an independent check of the argument meaning.

Positive F quantiles satisfy q(p;d1,d2)*q(1−p;d2,d1)=1 for interior probabilities. Both the complement and the degree swap are necessary. The saved advanced check returns approximately one, with a small binary floating-point residual retained in the raw evidence.

To work in upper-tail log form, use R.QF(LN(0.05),5,10,FALSE(),TRUE()). Do not pass LN(p) without setting log_p, or supply a positive ordinary probability with log_p TRUE. Fractional degrees such as 2.5 and 7.5 remain fractional.

The saved advanced-check result for =R.QF(.95,5,10)*R.QF(.05,10,5) was 1.

The lower probability zero returns zero. Lower probability one corresponds to an infinite endpoint and produces #NUM!; upper-tail endpoints reverse these roles. Outside [0,1] ordinary probabilities, positive log probabilities and nonpositive degrees also produce #NUM!.

An empty first argument becomes zero; with default tail it returns zero. Nonnumeric text gives #VALUE! and incorrect arity gives #N/A. Critical values only describe the chosen distribution; they do not establish the assumptions behind a variance test.

F5 is genuinely empty, rather than a cell containing an empty string.

• Current worksheet callback
• Tested-version worksheet callback
• Current qf calculation
• Tested-version qf calculation
• Nonfinite worksheet-value handling
• Statistical Functions From R plugin declaration

The relevant complete worksheet callback and main calculation helper are unchanged between the inspected versions. That does not establish later-version numerical execution. Both stale and uncached SUM controls recalculated correctly. Native XML preserves the R.* identities. The secondary ODF export keeps these calls in the ORG.GNUMERIC namespace; it does not establish execution in another product. GUI entry, other locales and other spreadsheet products were not tested.

FINV, FDIST, R.QGAMMA.