[Error] Validate transformed params

[ohspc89]

Hello, thank you very much for porting the examples of the book (Bayesian Cognitive Modeling) to Stan!

I have run the code: PsychophysicalFunction2_Stan.R.

When I run it, I get the same message repeatedly:

Chain 1: Exception: validate transformed params: z[i_0__][i_1__] is -2147483648, but must be greater than or equal to 0 (in 'model5d4e936bf38_a13a5b2b18daad6edd23eac3600fb7d2' at line 57

Then sampling is not done. I am a newbie to Stan and just learning from scratch. However, if anyone can check this issue, I would much appreciated it!