Reggies Linear Regression

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#1

Hello Everyone,
I was doing the Reggies linear regression challenge and couldn’t figure out the difference between

def calculate_all_error(m, b, datapoints): total_error = 0 for point in datapoints: point_error = calculate_error(m, b, point) total_error += point_error return total_error

and

def calculate_all_error(m,b,datapoints): error_total=0 for point in datapoints: point_error=calculate_error(m,b,point) print("point error",point_error) error_total+=point_error print(" error total",error_total) return error_total

When I print out every step, I can see that the loop works in the first code but not in the second one. If anyone would be able to explain the difference it would be much appreciated!

#2

Can we have a link to the lesson?

#3

https://www.codecademy.com/courses/learn-python-3/informationals/python3-reggies-linear-regression
that’s the link but it’s on jupyter notebook so you’d have to download the zip file.
I’ve just copied all previous code hopefully that helps.

def get_y(m, b, x): y = m*x + b return y get_y(1, 0, 7) == 7 get_y(5, 10, 3) == 25 def calculate_error(m, b, point): x_point, y_point = point y = m*x_point + b distance = abs(y - y_point) return distance #this is a line that looks like y = x, so (3, 3) should lie on it. thus, error should be 0: print(calculate_error(1, 0, (3, 3))) #the point (3, 4) should be 1 unit away from the line y = x: print(calculate_error(1, 0, (3, 4))) #the point (3, 3) should be 1 unit away from the line y = x - 1: print(calculate_error(1, -1, (3, 3))) #the point (3, 3) should be 5 units away from the line y = -x + 1: print(calculate_error(-1, 1, (3, 3))) datapoints = [(1, 2), (2, 0), (3, 4), (4, 4), (5, 3)] def calculate_all_error(m, b, datapoints): total_error = 0 for point in datapoints: point_error = calculate_error(m, b, point) total_error += point_error return total_error
#4

The return in the first one is outside the for-loop, so it happens after the loop finishes running.
The return in the second one is inside the for-loop, so it does one iteration of the loop (meaning the error for one point), and then does return total_error, which ends the function.

#5

That is very helpful. I would assume the second return would return a value for every iteration but as far as I understand what you’re saying is when the loop hits the return function it does not loop through any more?

#6

Yes. The loop (and the function) stops when it reaches return.