The calculator's z-scores come from lookup tables exported from the R models. This page recomputes a set of reference children in your browser and compares every value with R.
Ten children were drawn at random (fixed seed) from the reference group for each level of the aorta. For each child, R computed two z-scores: one from the full model (height, weight for height, age and sex) and one from the height-and-sex model used when weight is missing. Those R values come from the exported tables, which were themselves checked against the gamlss fit to within 0.0001.
This page loads the same tables, recomputes all of those z-scores with the calculator's own code, and compares them. A difference under 0.001 counts as a match. The largest difference is on the order of 0.0001, from interpolating between table points and from rounding the R values to four decimals. Model tables dated —.
| Level | Sex | Age (y) | Height (cm) | Weight (kg) | D (mm) | z full, R | Browser | Δ | z ht+sex, R | Browser | Δ |
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The test cases are in tests/root_bccg_testcases.csv; the R script that made them is R/export_bccg.R.
The comparison table also shows Lauzon-Schnittka z-scores. The browser code is a port of the authors' own R function, z_score(), and its coefficients, spline knots and WHO BMI tables are read out of that function by R/export_ls_model.R. The same script runs z_score() on 44 children across ages (1 day to 18.9 years), builds (very lean to BMIz beyond +5) and both sexes; those values are compared here with the browser, together with the median and the z = +2 diameter found by inverting z_score() in R.
| Sex | Age (y) | Height (cm) | Weight (kg) | BMIz, R | Browser | SOV z, R | Browser | STJ z, R | Browser | AAo z, R | Browser |
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