Code from: The effect of long-range linkage disequilibrium on allele-frequency dynamics under stabilizing selection

Stabilizing selection on a polygenic trait reduces the trait's
genetic variance by (i) generating correlations (linkage disequilibria)
between opposite-effect alleles throughout the genome, and (ii) selecting
against rare alleles at loci that affect the trait, eroding heterozygosity
at these loci. Here, we show that the linkage disequilibria, which
stabilizing selection generates on a rapid timescale, slow down the
subsequent allele-frequency dynamics at individual loci, which proceed on
a much longer timescale. Exploiting this separation of timescales, we
obtain expressions for the expected per-generation change in minor-allele
frequency at individual loci, as functions of the effect sizes at these
loci, the strength of selection on the trait, its variance and
heritability, and the linkage relations among loci. Using whole-genome
simulations, we show that our expressions predict allele-frequency
dynamics under stabilizing selection more accurately than the formulae
that have previously been used for this purpose. Our results have
implications for understanding the genetic architecture of complex traits.