R.PCHISQ Function (Gnumeric)

• Introduced: First release not established; present in the retained 1.12.57 source.
• 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.PCHISQ returns a chi-square cumulative probability by default. Setting lower_tail to FALSE selects the right tail. This differs from a legacy function whose name may imply a fixed right-tail convention, so set the tail explicitly when translating formulas. Versioned function help.

=R.PCHISQ(x,degrees_freedom[,lower_tail[,log_p]])

• x: cutoff; ordinary positive-degree models have lower-tail probability zero for x≤0.
• degrees_freedom: required positive real value; fractional values are used without integer truncation.
• lower_tail: optional TRUE; FALSE returns P(X>x).
• log_p: optional FALSE; TRUE returns the natural logarithm of the selected probability.

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; invalid-model observations are identified separately below. Results are rounded to twelve decimal places, or thirteen significant digits for small nonzero values. This is presentation precision, not a universal accuracy guarantee.

At x=2 with 2 degrees of freedom, the lower tail is approximately 0.632120558829, and the upper tail is 0.367879441171. The upper-tail expression reduces to EXP(−1).

At x=4 with 4 degrees of freedom, the cumulative probability is approximately 0.593994150290. With x=2 and 2.5 degrees of freedom it is approximately 0.526211220357; substituting 2 or 3 degrees would change the model.

The chi-square CDF is the gamma CDF with shape ν/2 and scale 2. The saved advanced check compares these parameterizations at x=4 and ν=4.

A right-tail chi-square test can use =R.PCHISQ(statistic,df,FALSE()) when its model and degrees of freedom are appropriate. This function only evaluates the supplied distribution; it does not establish the test assumptions. For the x=2,ν=2 example, the log upper-tail probability is exactly −1 to the shown precision.

The saved advanced-check result for =R.PCHISQ(4,4)-R.PGAMMA(4,2,2) was 0.

Require degrees_freedom>0 for the continuous distribution. The source’s zero-degree limit branch returned 0 at x=0 and 1 at x=1; those are not ordinary chi-square probabilities for a valid positive-degree model. Negative degrees produced #NUM!.

For valid degrees, log lower-tail probability at zero is −∞ and appears as #NUM!; log upper-tail probability there is 0. A blank cutoff is converted to zero. The boundary rows distinguish these cases from text and argument-count errors.

F5 is genuinely empty, rather than a cell containing an empty string. #NUM! can represent an unrepresentable infinite mathematical endpoint as well as an invalid numeric domain; the distinctions above matter.

• Current worksheet callback
• Tested-version worksheet callback
• Current pchisq calculation
• Tested-version pchisq calculation
• Current pgamma calculation
• Tested-version pgamma 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. Secondary ODF export maps two-argument R.DCHISQ to CHISQDIST with FALSE, R.PCHISQ to CHISQDIST, and R.QCHISQ to CHISQINV; additional arguments retain ORG.GNUMERIC names. These storage mappings do not establish execution in another product. GUI entry, other locales and other spreadsheet products were not tested.

CHIDIST, CHIINV, GAMMADIST.