# Implementing Cost function

In my implementation of finding the total cost in the week 2 homework, my code is passing the first 4 test cases but not the 5th. When I run the code in Jupyter I get 2.925 instead of 4.525. When I run the same code in PyCharm with which I am more familiar I get 3.9 instead of 4.525.

Any thoughts on what might be the problem with case 5?

Common issues are:

• mistakes in indentation.
• mistakes in parenthesis grouping.

I think all my indentations and parenthesis are correct.

{moderator edit: code removed}

# UNQ_C1

``````def compute_cost(x, y, w, b):
# moderator edit: code removed
``````

The 2 and m do have an asterisk between them

Please do not post your code on the forum. Thatâ€™s not allowed by the course community standards.

If a mentor needs to see your code, weâ€™ll ask you to send it via a private message.

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Note: Please review the equation for the cost calculation - specifically where the â€ś1/(2*m)â€ť factor is applied. It should be outside the summation - yours is inside.

Why does this matter? It is distributive. Whether I choose to apply 1/2m term by term or after the summation should not yield a new answer

Youâ€™re probably correct, my first thought was a recursive application of the `1/(2*m)` scaling for every iteration, giving a result more like `1/(2*m^2)`. But on further review, thatâ€™s not the case.

(edited)

The issue with your code is that it redefined the variable x, when you wrote this:
`x[i] = ...`

I set x[i] = w*x[i] + b, but Iâ€™m not sure why this would be the problem.
What I believe my code does is for each value in x, multiplies x by the weight and adds the bias. This becomes the new value of x[i]
Then it takes this value and computes 1/2m cost^2 and adds this to the total.

What is strange is in my own program I get 3.9 and in jyupter notebook I get 2.925.

I donâ€™t see how changing x[i] is effecting my answer because I use this updated value to represent f_wb

You used the x[i] value to compute w*x + b, then you overwrote the original value in x[i].

If you ever need that value back, itâ€™s gone forever.

Try using another local variable name and see if it helps.

Iâ€™ll review your notebook if you send it to me via a private message.

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