Modern R Programming Cookbook

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The rxImport() function from RevoScaleR creates the XDF file and stores metadata for each column. The important thing is that the newly created xdfFile object is not in the R session’s memory; rather the object just points to the location of the file in the persistent storage. You can call the file and perform further processing tasks. For example, if you want to see the variable's information, then rxGetInfo() will be useful. Here is some example code for seeing the variable's information:

    rxGetInfo(xdfFile, getVarInfo = TRUE) File name: D:\AllSync\Drive\Book-3\codeBundle\ch9\USAirlines2016.xdf Number of observations: 5562425 Number of variables: 9 Number of blocks: 12 Compression type: zlib Variable information: Var 1: YEAR, ...