[DynareDev] Bug in getPowerDeriv.m

Dear all,

There is a bug in getPowerDeriv. In rare cases such as entering x^(alppha-1) with x=0 in steady state and alpha=2 the derivative is wrong. The reason is that the first condition in getPowerDeriv checks whether x=0 and then sets the derivative to 0 as the derivative is p*0^(p-1) which is 0 if p~=1. But this is wrong if the exponent is p=1 as it then is 1*0^0=1.

I pushed a fix to git where the first condition checks whether p=1. This also affects the 4.2 branch.

Best,

Johannes

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Johannes Pfeifer

Haußerstr. 29

72076 Tübingen

Tel.: +49-(0)7071-6396184

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jpfeifer@gmx.de