rolling() for moving windows in Pandas - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the rolling() function in pandas do?

It creates a moving window over data, allowing calculations like sums or averages on subsets of data that slide over the dataset.

beginner

How do you specify the size of the moving window in rolling()?

You set the window size by passing an integer to rolling(window=), which defines how many data points are included in each window.

intermediate

What happens if the window size is larger than the available data points at the start?

By default, the result is NaN for those positions because there isn't enough data to fill the window.

beginner

How can you calculate the moving average of a pandas Series using rolling()?

Use series.rolling(window).mean() where window is the size of the moving window.

intermediate

What is the difference between rolling() and expanding() in pandas?

rolling() uses a fixed-size window that moves over data, while expanding() uses an increasing window starting from the first data point.

What does df['col'].rolling(window=3).sum() compute?

A Sum of every 3 consecutive values in 'col'

B Sum of all values in 'col'

C Sum of first 3 values only

D Sum of values skipping every 3rd value

The rolling sum with window=3 calculates the sum of each group of 3 consecutive values as the window moves.

If you want to avoid NaN values at the start when using rolling(), what parameter can you use?

A skipna=False

B window=0

C min_periods=1

D center=True

Setting min_periods=1 allows calculations with fewer data points than the window size, reducing NaN at the start.

What does the center=True option do in rolling()?

A Centers the data values

B Centers the window label on the current row

C Centers the output DataFrame

D Centers the index

With center=True, the window is centered on the current row instead of being right-aligned.

Which of these is NOT a valid aggregation function used with rolling()?

A mean()

B sum()

C median()

D plot()

plot() is not an aggregation function; rolling() expects functions like mean, sum, median.

What type of data structure does rolling() work on in pandas?

A Series and DataFrame

B Only Series

C Only DataFrame

D List

rolling() works on both pandas Series and DataFrame objects.

Explain how the rolling() function works in pandas and give an example of calculating a moving average.

Think about how you slide a small window over your data to calculate averages.

Describe the difference between rolling() and expanding() windows in pandas.

One window size stays the same, the other grows as you move through data.