chi2cdf — Evaluate the chi-square cumulative distribution function.
chi2cdf(x,nu) evaluates the chi-square CDF at x for degrees of freedom nu. chi2cdf(x,nu,"upper") returns the complementary upper-tail probability.
Syntax
p = chi2cdf(x, nu)
p = chi2cdf(x, nu, "upper")Inputs
| Name | Type | Required | Default | Description |
|---|---|---|---|---|
x | Any | Yes | — | Evaluation point. |
nu | Any | Yes | — | Degrees of freedom parameter. |
tail | StringScalar | Yes | "upper" | Upper-tail selector (`"upper"`). |
Returns
| Name | Type | Description |
|---|---|---|
y | NumericArray | Distribution function value. |
Errors
| Identifier | When | Message |
|---|---|---|
RunMat:chi2cdf:InvalidArgument | Inputs are nonnumeric, sizes are incompatible, or too many arguments are supplied. | normal distribution: invalid argument |
RunMat:chi2cdf:Internal | Internal tensor conversion or allocation fails. | normal distribution: internal error |
How chi2cdf works
xandnusupport scalar expansion and matching array shapes.- Typed-integer
xandnuvalues from all eight classes are mode-gated RunMat extensions and must lie within the exact-integer binary64 range. - Single-precision inputs produce single-precision output; otherwise output is double precision.
numust be positive; invalid parameters produceNaNoutputs.- Negative
xvalues return zero for the lower tail and one for the upper tail. - The computation uses regularized incomplete gamma functions.
Example
Evaluate chi-square CDF
p = chi2cdf(3,5)Expected output:
p = 0.3000Using chi2cdf with coding agents
Open a RunMat example with live inputs, then ask the agent to explain how chi2cdf changes the result.
Run a small chi2cdf example, explain the result, then change one input and compare the output.
FAQ
Why use the upper-tail form?⌄
The upper-tail form computes the complementary incomplete-gamma value directly, which is more stable for extreme upper tails than 1 - chi2cdf(...).
Related Stats functions
Summary
binocdf · boxplot · cdf · cdfplot · corr · corrcoef · corrcov · cov · cov2corr · dummyvar · ecdf · filloutliers · fitdist · geomean · grpstats · harmmean · icdf · isoutlier · kstest · kurtosis · lsline · mad · mode · nanmax · normalize · normcdf · norminv · normpdf · onehotdecode · onehotencode · pdf · prctile · quantile · refline · rmse · skewness · tabulate · tcdf · tiedrank · tinv · tpdf · ttest2 · wblinv
Ml
bayesopt · classify · confusionmat · crossvalind · cvpartition · fitclinear · fitctree · fitlm · kmeans · knnsearch · lasso · lassoglm · linkage · lscov · mnrfit · optimizableVariable · pdist · pdist2 · perfcurve · predict · regress · ridge · squareform · test · training · tsne
Random
binornd · bootstrp · datasample · dividerand · exprnd · gamrnd · lhsdesign · mvnrnd · normrnd · random · randsample · rng · trnd · unidrnd · unifrnd · wblrnd
Hist
Open-source implementation
Unlike proprietary runtimes, every RunMat function is open-source. Read exactly how chi2cdf is executed, line by line, in Rust.
- View the source for chi2cdf in Rust on GitHub
- Learn how the RunMat runtime works
- Found a bug? Open an issue with a minimal reproduction.
About RunMat
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