David Smith walks us through various ways to integrate R and Excel:
If you’re familiar with analyzing data in Excel and want to learn how to work with the same data in R, Alyssa Columbus has put together a very useful guide: How To Use R With Excel. In addition to providing you with a guide for installing and setting up R and the RStudio IDE, it provide a wealth of useful tips for working with Excel data in R, including:
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To import Excel data into R, use the readxl package
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To export Excel data from R, use the openxlsx package
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How to remove symbols like “$” and “%” from currency and percentage columns in Excel, and convert them to numeric variables suitable for analysis in R
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How to do computations on variables in R, and a list of common Excel functions (like RAND and VLOOKUP) with their R equivalents
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How to emulate common Excel chart types (like histograms and line plots) using R plotting functions
 
David also shows how to run R within Excel.  One of the big benefits of readxl is that it doesn’t require Java; most other Excel readers do.