ibd_kappa and sibs with inbred, unrelated, parents

[thoree]

ibd_kappa suprises me below, not ibd_identity:

library(ribd, quietly = TRUE)
x = nuclearPed(2, father = "FA", mother = "MO",  children = c("B1", "B2"))
f1 = 0.1
f2 = 0.2
f = c(f1, f2)
founder_inbreeding(x, c("FA", "MO")) = f
ibd_kappa(x, ids = c("B1", "B2"))
#> Inbred individuals: B1, B2
#> The kappa coefficients are undefined for inbred individuals.
#> [1] NA NA NA

f00 = (1-f1)*(1-f2)
f10 = f1*(1-f2)
f01 = (1-f1)*f2
f11 = f1*f2

k0 = f00*0.25
k1 = f00*0.5+f10*0.5+f01*0.5
k2 = f00*0.25+f10*0.5+f01*0.5+f11
k = c(k0, k1, k2)
j = ibd_identity(x, ids= c("B1", "B2"))[9:7]
k-j
#> [1] -1.387779e-16  2.775558e-16  0.000000e+00

^{Created on 2019-01-22 by the reprex package (v0.2.1)}

[magnusdv]

Thanks. This was caused by rounding errors; the current version should be more robust.