C3_W2_Collaborative_RecSys_Assignment: Wrong data for Regularization

Course Q&A Machine Learning Specialization Unsupervised Learning, Recommenders, Reinforcement
1

Hi,
I have an issue for the C3_W2_Collaborative_RecSys_Assignment
Exercise 1
In the steps it is asked to compute cofi_cost_func with and without regularization
In the function towards the end, where J is computed,
As it asks to compute J without regularization first followed by with regularization, and since it is the same function call,
I added like this
if(lambda_ == 0):
J +=
else :
J +=

Is this approach correct?

I dont get any syntax error, but the value of J that is returned WITH regularization is wrong.

I am getting 144.43, whereas expected is 28.09

Can you please help me where I am going wrong?

Regards
Ravikiran

2

That’s not a necessary approach.

I recommend you implement only the code for the regularized cost, and if lambda = 0, then that contribution will be zero because it is a multiplier.

That indicates your calculation is incorrect.

3

But then I am getting error for the previous one where we calculate WITHOUT regularization where the expected output is 13.67 which I got with the different formula?
I guess there are two different formulas for with and without.
Is that not correct?

4

There is only one equation for the cost.

This image is from Section 4.1 of the notebook:

image
image810×171 13.1 KB

The part labeled A is the unregularized cost.

The part labeled B is the regularized portion of the cost.

If the cost function is called with the lambda parameter set to 0, then the B portion will compute to 0, so the function returns only the unregularized cost.

If you don’t get the correct results for the A portion, there is an error in your code.

5

I am kind of little lost.
From the “hints” portion of the exercise, it showed two different equations for w/o regularization and with regularization.
As per your tip, I should still use the equation for “regularization” and since lambda will be 0, it should work for w/o regularization also?

Let me try

Ravikiran

6

I am not sure if I am getting the correct value after following the equation.
I am stuck at this place.
I am aware that I am not supposed to paste the code here, but please delete it after I get the fix for this.
Please let me know what I did below is correct?

{mentor edit: code removed}

With regularization, I am getting a value of 302.13, while expected is 28.09

Please help

Ravikiran

7

Please do not share your code on the forum. That’s not allowed by the Code of Conduct.

You can send me your code via a private message, I’ll send you instructions in a moment.

Also note that the “preformatted text” tag should be used so that your code indentation is preserved.

8

Thank you, yes I am kind of aware not to do. Probably I should have asked how to do private message.
Sorry and thank you

9

Report back for students who find this thread later:

  • Be sure that if you compute the regularized cost for all values of X and W, that you do so only once (outside of any nested for-loops).