Challenges with week 3 test Q.4

Course Q&A Machine Learning Specialization Supervised ML: Regression and Classification
1

I have been looking through the labs to see if I can find examples for Q4. Because of the two for loops:
for i in range (m):
for j in range (n):
That we are required to loop through X and w, and then cast b, rather than use dot.product.

I am getting the following error message and am stuck.

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Happy to share my code to see if someone can point out the error.

The hint suggests"*

  • Calculate f_wb (exactly how you did it in the compute_cost function above)*

The z_wb term in the cost function utilised dot product and sigmoid and doesn’t require the use of the i and j loops. I am confused.

Any pointers would be appreciated.

2

Hi Ian, Welcome to the community!

It looks like the issue arises from how you’re handling the bias term b and the term z_wb in your predict function. Specifically, the error TypeError: 'float' object is not iterable indicates that you might be attempting to add a scalar value (your bias term b) to a NumPy array (probably z_wb) in a way that Python doesn’t recognize as valid. The way you wrote z_wb += b may have confused if z_wb is not initialized properly, or if the dimensions of b and z_wb are incompatible.

As you mentioned, there are two loops iterating over m (number of examples) and n (number of features). You need to make sure that you’re calculating z_wb as a scalar for each example i in m. You can achieve this by summing over the dot product of the weights and features and adding the bias b afterward.

The hint about calculating f_wb is suggesting you follow the same process as in the cost function:
- Calculate the linear combination of inputs and parameters z_wb = np.dot(...) + ... where X[i] corresponds to the ith example
- Calculate the sigmoid of the linear combination: f_wb = sigmoid(z_wb)

I hope this helps!

3

Thank you. Q4 solved. but now I am getting this error with Q. 5.

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4

The syntax of that line looks okay. I suspect the problem in the preceding few lines. Python doesn’t always highlight the line with the actual error.

5

As @danieljhand mentioned, this error indicates that there is probably a small typo or syntax error somewhere in the lines above it. Here are a few things to check:

  • Make sure that cost_without_reg and reg_cost are defined correctly.

  • Make sure the parentheses in reg_cost are properly enclosed.

6

Python throws a syntax error at the point where it gives up trying to make sense of the code.

So the error always lies somewhere prior to the error marker.

7

ky you for your help