Trend lines on scatter plots in Matplotlib - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a trend line in a scatter plot?

A trend line is a straight or curved line drawn through a scatter plot to show the general direction or pattern of the data points.

beginner

How do you calculate a simple linear trend line for scatter plot data?

You calculate the best-fit line using linear regression, which finds the line that minimizes the sum of the squared distances between itself and all data points.

beginner

Which Python library is commonly used to add trend lines to scatter plots?

Matplotlib is commonly used for plotting, and NumPy or SciPy can be used to calculate trend lines with linear regression.

beginner

What does the slope of a trend line represent?

The slope shows how much the y-value changes for each unit increase in the x-value, indicating the strength and direction of the relationship.

beginner

Why is it useful to add a trend line to a scatter plot?

A trend line helps to see the overall pattern or relationship in noisy data, making it easier to understand and explain.

What function in NumPy can be used to calculate the coefficients for a linear trend line?

A numpy.polyfit()

B numpy.mean()

C numpy.random()

D numpy.sort()

numpy.polyfit() fits a polynomial (degree 1 for linear) to data points, giving coefficients for the trend line.

In matplotlib, which function is used to create a scatter plot?

A plt.plot()

B plt.scatter()

C plt.bar()

D plt.hist()

plt.scatter() creates scatter plots by plotting individual points.

What does a positive slope in a trend line indicate?

A As x increases, y decreases

B No relationship between x and y

C As x increases, y increases

D Data points are random

A positive slope means y values go up as x values go up.

Which of these is NOT a reason to add a trend line to a scatter plot?

A To make the plot colorful

B To predict future values

C To highlight the general pattern

D To summarize data relationship

Trend lines are for analysis, not for decoration or color.

What degree polynomial fits a straight line trend?

A 3

B 0

C 2

D 1

Degree 1 polynomial is a straight line.

Explain how to add a linear trend line to a scatter plot using matplotlib and numpy.

Think about fitting a line and then drawing it over the scatter points.

Describe why trend lines are helpful when analyzing scatter plot data.

Consider what you want to learn from many scattered points.