R.DEXP 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.DEXP returns exponential density at x. Its scale is the mean of the ordinary positive-scale distribution. give_log=TRUE requests natural log density. Density is not a cumulative probability or a probability assigned to one exact continuous value. Versioned function help.

=R.DEXP(x,scale[,give_log])

• x: observation.
• scale: required positive scale parameter.
• give_log: optional, FALSE by default. TRUE returns natural log density.

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

These self-contained formulas were recalculated natively and checked against independent mathematics. 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 a model with scale 2, the rate is 0.5 and the density at x=2 is exp(−1)/2≈0.183939720586. At x=0 the density is 0.5. Negative x has density zero because it lies outside the model’s support.

If a separate model specifies rate λ, convert with scale=1/λ. For instance, rate 0.5 corresponds to =R.DEXP(2,2), not =R.DEXP(2,0.5). The parameter’s units are the same as x.

For x≥0, density is exp(−x/scale)/scale and its natural log is −x/scale−LN(scale). Multiplying density by scale gives the survival probability at the same x. The executed check =R.DEXP(2,2)*2-R.PEXP(2,2,FALSE()) is zero.

At x=1600 with scale 2, native density underflows to zero, while log density remains approximately −800.693147180560. That log form is useful when adding contributions from many observations. It does not turn a zero-support negative x into a finite log density.

The saved advanced-check result for =R.DEXP(2,2)*2-R.PEXP(2,2,FALSE()) was 0.

Scale zero or negative gives #NUM!. A negative x with give_log=TRUE also gives #NUM!: the mathematical log of zero is −infinity, which is not a finite worksheet result. Use positive scale for the ordinary distribution. Numeric text may convert; nonnumeric text gives #VALUE!. The explicit log flag should be TRUE/FALSE.

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 dexp calculation
• Nonfinite worksheet-value handling
• Statistical Functions From R plugin declaration

The relevant worksheet callback is unchanged between the inspected versions. That does not establish later-version numerical execution. Both stale and uncached SUM controls recalculated correctly. Native XML identities were checked; secondary ODF exports retain these functions with the ORG.GNUMERIC namespace. GUI entry, other locales and other spreadsheet products were not tested.

EXPONDIST, LN, EXP.