zscore

std.stats.zscore · Level L1

Standard scores: each element's distance from the mean, in standard deviations. Calls std.

(xᵢ − x̄) / σ

Signature

zscore(x: f64[n]) → f64[n]

Structure

The function as NOVA stores it: one box per input, operation and output, and arrows that carry values. A double border marks a call to another library function; select it to open that function.

xf64[n]MeanmustdsSubtractdDividezzf64[n]
  • input
  • operation
  • constant
  • call
  • output

Verification

  • Signature proven by NOVA’s shape solver, for every size.
  • Agrees with the reference (x - x.mean()) / x.std() to 80 digits (100-digit arithmetic), on all 40 test cases.
  • All 191 float64 results inside the running error bound; the closest uses 20% of it.
  • Interpreter and NumPy backend return bit-identical results.
Accuracy in detail
correctly rounded (the float64 nearest the exact value)
60%
bit-equal to the NumPy formula in float64
100%
largest error, in units in the last place
44

Large ulp counts appear only where cancellation drives a result toward zero; the absolute error is still inside the bound.

Identity

Calls
std
Called by
—
sha256:b0b89d5d97a1925ce1c5e581897ebbd69f541b4e08e8c702ac0a8408331e80a5

The semantic hash of the graph. It changes when the program changes, and never when only its documentation does.