# Course 1 Week 3 Exercise 5 the cost function

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How did you guys implement the cost function? See my attempt and help

The last term is incorrect. Please fix it keeping in mind that `A2` is in probability scale.
Don’t forget to remove code from your post.

Thanks! I made the correction as follows:

[code removed - moderator]

it worked.

Term 1 logprobs: [[-0.69268589 -0. -0. ]] Term 2: [[0. 0.50014169 0.49976037]]

TypeError Traceback (most recent call last)
in
1 A2, t_Y = compute_cost_test_case()
----> 2 cost = compute_cost(A2, t_Y)
3 print("cost = " + str(compute_cost(A2, t_Y)))
4
5 compute_cost_test(compute_cost)

in compute_cost(A2, Y)
27 print(‘\n\n’)
28
—> 29 cost = (-1/m) * np.sum((logprobs),((1-Y)*np.log(1-A2)))
30
31 # debug

<array_function internals> in sum(*args, **kwargs)

/opt/conda/lib/python3.7/site-packages/numpy/core/fromnumeric.py in sum(a, axis, dtype, out, keepdims, initial, where)
2227
2228 return _wrapreduction(a, np.add, ‘sum’, axis, dtype, out, keepdims=keepdims,
→ 2229 initial=initial, where=where)
2230
2231

/opt/conda/lib/python3.7/site-packages/numpy/core/fromnumeric.py in _wrapreduction(obj, ufunc, method, axis, dtype, out, **kwargs)
88 return reduction(axis=axis, out=out, **passkwargs)
89
—> 90 return ufunc.reduce(obj, axis, dtype, out, **passkwargs)
91
92

TypeError: only integer scalar arrays can be converted to a scalar index

@Brendon_Wolff-Piggot
Please read the markdown for the exercise. Your computation of `logprobs` and eventually the `cost` is incorrect.
If it helps, see the definition of `J` just above the writeup for `Exercise 5 - compute_cost` section.

I’m sure you’re right. I just didn’t come right looking at the code at the top of the exercise.

I ended up going back to the line I used in the backpropagation assignment and it worked immediately. Is there a place to look at model answers when the assignment is closed?

No, sorry, there are no “official solutions” that you can use as a reference. My guess is that this is because of concerns about cheating. Where would they put those in such a way that you can only see them after you’ve completed the exercise and how do they prevent them from being shared?

Onwards and upwards then…