error in setting up for hard test

Working fine like in example link: http://bl.ocks.org/anshul96go/raw/fba7546582315e27b637dfeabe254e59/

gradient descent example given in medium tests is implemented using animint2. It is also giving the same error as my code

The R notebook of medium test in animint 2 It shows the errors occuring in using animint 2 which is automatically corrected by using animint