Random [uniform?] sudokus
A longer run of the R code of yesterday with a million sudokus produced the following qqplot.
It does look ok but no perfect. Actually, it looks very much like the graph of yesterday, although based on a 100-fold increase in the number of simulations. Now, if I test the adequation with a basic chi-square test (!), the result is highly negative:
> chisq.test(obs,p=pdiag/sum(pdiag)) #numerical error in pdiag
Chi-squared test for given probabilities
X-squared = 6978.503, df = 6, p-value < 2.2e-16
(there are seven entries for both obs and pdiag, hence the six degrees of freedom). So this casts a doubt upon the uniformity of the random generator suggested in the paper by Newton and DeSalvo or rather on my programming abilities, see next post!