This post shows how to use formulas to manipulate Library of Congress (LC) call numbers in Microsoft Excel. I demonstrated this technique as part of a presentation that I made at the Wrangling Library Data virtual conference last month.

An LC call number denotes the subject matter of a published resource, such as a book, as judged by a cataloger. In theory, by relying on call number data, libraries can measure the strengths and weaknesses of their collections, evaluate resource use, and assess the merits of prospective resource purchases. However, because call numbers often denote very specific topics, it can be challenging to convert them into categories that provide for insightful analysis.

I have created an Excel file that can quickly manipulate up to 20,000 call numbers, deriving multiple data points for each one. As illustrated in the image below, this utility file performs the following functions:

• It extracts the one- and two-letter classes that form the core of the LC classification.
• It generates two data points by way of numerical rounding: LC100 and LC Class + Number (Integer). Depending on the breadth of one’s data set, these derivatives provide for increasingly granular subject analysis.
• It translates the one- and two-letter classes into their corresponding descriptions.