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ProbabilityDistribution ​

A distribution given directly by its density pdfpdf, over x∈[min,max]x \in [min,max] (continuous) or x∈{min,…,max}x \in \{min,\ldots,max\} (discrete, step size 1).

ProbabilityDistribution(pdf, {x, min, max})continuous, density pdf(x) over [min, max].
ProbabilityDistribution(pdf, {x, min, max, 1})discrete, mass pdf(x) over {min, ..., max} — step size pinned to 1.
Typed signatures
TypePackageApplies
(any, list<any>) -> distributionstatisticsalways

Domain: Statistics

Details
  • pdfpdf is used AS WRITTEN, not renormalized — same as Wolfram's own ProbabilityDistribution, which does not renormalize its pdf argument either; it is the caller's responsibility that it already integrates/sums to 1.
  • PDF(v)=pdf∣x=vPDF(v) = pdf|_{x=v} (substitution) inside [min,max][min,max], 00 outside.
  • CDFCDF/MeanMean/VarianceVariance go through compute-engine's own native Integrate (continuous) or Sum (discrete): exact whenever those resolve to a closed form, and left UNEVALUATED (not approximated) when they don't — numeric approximation still reaches them through N, same as everywhere else in this package.
  • An arbitrary discrete step size (other than 1) is out of scope for this head.

Examples

Basic #

pdf(x) = 2x, a triangular density on [0,1].

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InPDF⁡(ProbabilityDistribution(2x,[x,0,1]),12)\operatorname{PDF}(\mathrm{ProbabilityDistribution}(2x, \bigl\lbrack x, 0, 1\bigr\rbrack), \frac{1}{2})Out11
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InPDF⁡(ProbabilityDistribution(2x,[x,0,1]),2)\operatorname{PDF}(\mathrm{ProbabilityDistribution}(2x, \bigl\lbrack x, 0, 1\bigr\rbrack), 2)Out00
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Inmean(ProbabilityDistribution(2x,[x,0,1]))\mathrm{mean}(\mathrm{ProbabilityDistribution}(2x, \bigl\lbrack x, 0, 1\bigr\rbrack))Out23\frac{2}{3}
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InVariance(ProbabilityDistribution(2x,[x,0,1]))\mathrm{Variance}(\mathrm{ProbabilityDistribution}(2x, \bigl\lbrack x, 0, 1\bigr\rbrack))Out118\frac{1}{18}
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InCDF⁡(ProbabilityDistribution(2x,[x,0,1]),12)\operatorname{CDF}(\mathrm{ProbabilityDistribution}(2x, \bigl\lbrack x, 0, 1\bigr\rbrack), \frac{1}{2})Out14\frac{1}{4}

a discrete uniform on {1,2,3,4} written by hand.

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InPDF⁡(ProbabilityDistribution(14,[x,1,4,1]),2)\operatorname{PDF}(\mathrm{ProbabilityDistribution}(\frac{1}{4}, \bigl\lbrack x, 1, 4, 1\bigr\rbrack), 2)Out14\frac{1}{4}
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Inmean(ProbabilityDistribution(14,[x,1,4,1]))\mathrm{mean}(\mathrm{ProbabilityDistribution}(\frac{1}{4}, \bigl\lbrack x, 1, 4, 1\bigr\rbrack))Out52\frac{5}{2}

Integrate has no closed form here, so Mean stays unevaluated rather than approximate.

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Inmean(ProbabilityDistribution(sin⁡(xx),[x,0,1]))\mathrm{mean}(\mathrm{ProbabilityDistribution}(\sin(x^{x}), \bigl\lbrack x, 0, 1\bigr\rbrack))Outmean(ProbabilityDistribution(sin⁡(xx),[x,0,1]))\mathrm{mean}(\mathrm{ProbabilityDistribution}(\sin(x^{x}), \bigl\lbrack x, 0, 1\bigr\rbrack))
About
Examples8

See also: HistogramDistribution, PDF, CDF, Mean