Problems with the BTYD walk-through fixed

If you're going through the Buy 'Til You Die package's walk-through, you are bound to get stuck in a couple of places. Here are fixes to some of those problems.

Page 5
Warning message:
In cbind(f, r, T) : number of rows of result is not a multiple of vector length (arg 2)

This error occurs because the walk through specifies tot.cbt as tot.cbt = dc.CreateFreqCBT(elog). This is incorrect and should be tot.cbt = dc.CreateFreqCBT(elog.cal). After making that change, the error is fixed.

Page 6
Error: could not find function "pnbd.PlotDropoutHeterogeneity"

pnbd.PlotDropoutHeterogeneity(params) doesn't work because the function name has changed. Replace it with pnbd.PlotDropoutRateHeterogeneity(params) and it works fine.

Page 8
Error in pnbd.PAlive(params, x, t.x, T.cal) : could not find function "hyperg_2F1"

If you haven't loaded the package "gsl", the function pnbd.ConditionalExpectedTransactions will throw an error. It's easily fixed by loading the gsl library.

Faster BTYD

The R-library "Buy 'Til You Die" for customer equity forecasting looked promising, but I quickly realised that the implementation relies heavily on loops and is not suited for any data set bigger than a couple of thousand rows.

To speed things up, I switched out a couple of the loops for some data.table magic. Here it is, about 10000X faster than the original, but there is still some room for improvement.

If you're having trouble getting the BTYD package to run, take a look at this post for fixes.