Sea Level Predictor FAIL: test_plot_lines (test_module.LinePlotTestCase)

Python
1

Hello, I’m having some trouble trying to fix this issue with my plot. Apparently there is a mismatch in shape and in the expected lines from the arrays. However, when looking at my graph I feel like it looks exactly as it is supposed to look like, as they ask for two lines predicting the sea level behavior for 2050.

This is my graph:

sea_level_plot

This is my code:

# Read data from file
df = pd.read_csv('epa-sea-level.csv')

# Create scatter plot
y = df['CSIRO Adjusted Sea Level']
x = df['Year']
plt.scatter(x, y)
plt.xlabel('Year')
plt.ylabel('Sea Level (inches)')
plt.title("Rise in Sea Level")

# Create first line of best fit
slp = linregress(x, y)
new = {'Year': 2050}
df = df.append(new, ignore_index=True)
y = df['CSIRO Adjusted Sea Level']
x = df['Year']
plt.plot(x, y, 'o')
plt.plot(x, slp[0] * x + slp[1])
plt.xlabel('Year')
plt.ylabel('Sea Level (inches)')
plt.title("Rise in Sea Level")

# Create second line of best fit
dfb = df[(df['Year'] >= 2000) & (df['Year'] < 2050)]
yb = dfb['CSIRO Adjusted Sea Level']
xb = dfb['Year']
slpb = linregress(xb, yb)
new = {'Year': 2050}
dfb = dfb.append(new, ignore_index=True)
yb = dfb['CSIRO Adjusted Sea Level']
xb = dfb['Year']
plt.plot(x, y, 'o')
plt.plot(x, slp[0] * x + slp[1])
plt.plot(xb, slpb[0] * xb + slpb[1])

# Add labels and title
plt.xlabel('Year')
plt.ylabel('Sea Level (inches)')
plt.title("Rise in Sea Level")

This is the error I’m getting:

AssertionError:
Arrays are not almost equal to 7 decimals
Expected different line for first line of best fit.
(shapes (135,), (171,) mismatch)
x: array([ 0. , 0.2204724, -0.4409449, -0.2322835, 0.5905512,
0.5314961, 0.4370079, 0.2165354, 0.2992126, 0.3622047,
0.4409449, 0.3740157, 0.5 , 0.6850394, 0.3031496,…
y: array([-0.542124 , -0.4790794, -0.4160349, -0.3529903, -0.2899457,
-0.2269011, -0.1638565, -0.1008119, -0.0377674, 0.0252772,
0.0883218, 0.1513664, 0.214411 , 0.2774556, 0.3405002,…

Ran 4 tests in 0.279s
FAILED (failures=1)

Challenge: Sea Level Predictor

Link to the challenge:

2

Hi @juanespal

I was just stuck with a similar problem and finally found the issue. Have a look at the test_plot_lines function in test_module.py: Here, all the points of the line that you plotted are compared to the expectation - and the expectation is that there is a value pair for all years 1880 to 2050 for the first line, and for all years 2000 to 2050 for the second line. So that’s why you get a shape mismatch. The test expects an array with 171 values, while you provided 135 only. While the plot looks perfectly fine, the underlying data is different.
Hope this helps!

3 Likes
3

Will definitely give it a try. Thanks for the help! Can’t help but think that the test should be changed, since it only seems to validate a single approach to a problem that can be solved in many different ways.

1 Like
4

Hello, I’ve managed to get it working. Had to do exactly as you said. Plotting each point was the way to go. Thank you so much!

5

Great :slight_smile:
I’m half way convinced that it’s part of the challenge to understand the test code… after all, a lot about working in programming is about reading other people’s code.

6

I’m getting a similar error.
“Expected different line for first line of best fit.
(shapes (170,), (171,) mismatch)”
How did you match the array lengths?

7

It is much easier if you open your own thread and post a link to your code.