Rolling mean and sum in Pandas - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a rolling mean in pandas?

A rolling mean calculates the average of values in a moving window over a series. It helps smooth out short-term fluctuations and highlight longer-term trends.

beginner

How do you calculate a rolling sum in pandas?

Use the rolling(window).sum() method on a pandas Series or DataFrame to get the sum of values within a moving window of specified size.

beginner

What does the window parameter specify in rolling calculations?

The window parameter sets the size of the moving window, i.e., how many consecutive values are included in each calculation.

intermediate

What happens to the first few values when using rolling mean with a window size of 3?

The first two values will be NaN because there are not enough data points to fill the window of size 3.

intermediate

How can you include the current row in the rolling window calculation?

By default, the rolling window includes the current row and previous rows up to the window size. You can adjust this with parameters like min_periods or center.

Which pandas method calculates the rolling mean?

A mean(window)

B rolling(window).sum()

C rolling(window).mean()

D sum(window)

The method rolling(window).mean() computes the rolling mean over the specified window.

If you use rolling(4).sum() on a Series, what does the number 4 represent?

A The size of the moving window

B The number of rows to skip

C The number of columns to sum

D The total sum of the Series

The number 4 is the window size, meaning the sum is calculated over 4 consecutive values.

What will be the output for the first value when using rolling(3).mean()?

A The mean of first 3 values

B The first value itself

C Zero

D NaN

The first value is NaN because there are not enough values to fill the window of size 3.

How can you change the rolling window to be centered on the current row?

A Set <code>min_periods=0</code>

B Set <code>center=True</code> in rolling()

C Use <code>shift()</code> method

D Use <code>sum()</code> instead of <code>mean()</code>

Setting center=True centers the window on the current row.

What does min_periods control in rolling calculations?

A Minimum number of observations in window to have a value

B Maximum window size

C Number of columns to include

D Number of rows to skip

min_periods sets the minimum number of data points required in the window to compute a result instead of returning NaN.

Explain how rolling mean and rolling sum work in pandas and why they are useful.

Think about how you might smooth noisy data or find running totals.

Describe how to use the rolling() method with parameters to customize the window behavior.

Consider how to adjust window size and alignment.