Google Finance in Historical Mode (WEEKLY): Extra Rows and Not Always Aligned to Fridays

This article will delve into a common issue encountered when using the GOOGLEFINANCE function in Google Sheets to query weekly closing prices. You might find yourself puzzled by unexpected results, including extra rows that don’t align with Fridays and missing data for specific weeks. We’ll explore the reasons behind this behavior and provide solutions to ensure accurate and reliable weekly data extraction.

Understanding the Challenge

When using the GOOGLEFINANCE function with the WEEKLY interval, you aim to retrieve data points that represent the closing price for each Friday. However, you may experience the following:

• Extra Rows: The function sometimes returns data for days other than Friday, leading to more data points than expected for a 52-week period.
• Missing Data: You might find that data for specific Fridays is absent, even when no major holidays or market closures occurred during those weeks.

Investigating the Cause

The issue stems from the way Google Finance handles historical data in a weekly context. While it aims to provide data points for Fridays, the system isn’t always consistent in aligning data precisely with weekly intervals. This can lead to the anomalies mentioned earlier.

Solutions for Reliable Weekly Data

Here are strategies to work around the inconsistencies and obtain the desired weekly closing prices:

1. Employing the WORKDAY and WEEKDAY Functions

The WORKDAY function helps adjust dates to account for weekends and holidays, while the WEEKDAY function identifies the day of the week. Combining these can help you force the start and end dates of your GOOGLEFINANCE query to fall on Fridays.

For example:

=GOOGLEFINANCE("INDEXSP:.INX", "close", 
SWITCH(WEEKDAY(TODAY()-364, 2), 1, TODAY()-365, 2, TODAY()-366, 3, TODAY()-367, 4, TODAY()-368, 5, TODAY()-364, 6, TODAY()-363, 7, TODAY()-362), 
SWITCH(WEEKDAY(TODAY(), 2), 1, TODAY()-1, 2, TODAY()-2, 3, TODAY()-3, 4, TODAY()-4, 5, TODAY(), 6, TODAY()+1, 7, TODAY()+1), 
"WEEKLY")

This formula ensures that the start and end dates are adjusted to the nearest preceding Friday.

2. Filtering Data for Fridays

After retrieving the data using GOOGLEFINANCE, you can filter the results to include only data points corresponding to Fridays. You can use the FILTER function along with the WEEKDAY function to achieve this.

For instance:

=FILTER(GOOGLEFINANCE("INDEXSP:.INX", "close", TODAY()-364, TODAY(), "WEEKLY"), WEEKDAY(GOOGLEFINANCE("INDEXSP:.INX", "date", TODAY()-364, TODAY(), "WEEKLY"), 2) = 5)

This formula will return only the closing prices for Fridays within the specified date range.

Best Practices for Reliable Data

Here are additional tips for ensuring accurate data extraction:

• Test Thoroughly: Experiment with different date ranges and formulas to understand how GOOGLEFINANCE behaves in specific scenarios.
• Consult Documentation: Refer to the official documentation of Google Sheets’ GOOGLEFINANCE function for detailed information and examples.
• Consider Alternatives: If you encounter persistent difficulties, explore alternative data sources or APIs that provide more reliable weekly data.

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By implementing these strategies and adhering to best practices, you can overcome the challenges associated with GOOGLEFINANCE and obtain accurate weekly closing prices for your financial analysis.