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rxMerge: Merge two data sources

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Description

Merge (join) two data sources on one or more match variables. The rxMerge function is multi-threaded. In local compute context, the data sources may be sorted .xdf files or data frames. In RxSpark compute context, the data sources may be RxParquetData, RxHiveData, RxOrcData, RxXdfData or RxTextData.

Usage


  rxMerge( inData1, inData2 = NULL, outFile = NULL, matchVars = NULL, type = "inner",
           missingsLow = TRUE, autoSort = TRUE, duplicateVarExt = NULL,
           varsToKeep1 = NULL, varsToDrop1 = NULL, newVarNames1 = NULL,
           varsToKeep2 = NULL, varsToDrop2 = NULL, newVarNames2 = NULL,
           rowsPerOutputBlock = -1, decreasing = FALSE, overwrite = FALSE, 
           maxRowsByCols = 3000000, bufferLimit = -1, 
           reportProgress = rxGetOption("reportProgress"), verbose = 0, 
           xdfCompressionLevel = rxGetOption("xdfCompressionLevel"), ... ) 

  rxMergeXdf( inFile1, inFile2, outFile, matchVars = NULL, type = "inner",
              missingsLow = TRUE,   duplicateVarExt = NULL,
              varsToKeep1 = NULL, varsToDrop1 = NULL, newVarNames1 = NULL,
              varsToKeep2 = NULL, varsToDrop2 = NULL, newVarNames2 = NULL,
              rowsPerOutputBlock = -1, decreasing = FALSE, overwrite = FALSE, 
              bufferLimit = -1, reportProgress = rxGetOption("reportProgress"), 
              verbose = 0, xdfCompressionLevel = rxGetOption("xdfCompressionLevel"), ... )

Arguments

inData1

the first data set to merge. In local compute context, a data frame, a character string denoting the path to an existing .xdf file, or an RxXdfData object. If a list of RxXdfData objects is provided, they will be merged sequentially. In RxSpark compute context, an RxParquetData, RxHiveData, RxOrcData, RxXdfData or RxTextData data source. If a list of data source objects is provided, they will be merged sequentially.

inFile1

the first data set to merge; either a character string denoting the path to an existing .xdf file or an RxXdfData object.

inData2

the second data set to merge. In local compute context, a data frame, a character string denoting the path to an existing .xdf file, or an RxXdfData object. Can be NULL if a list of RxXdfData objects is provided for inData1. In RxSpark compute context, an RxParquetData, RxHiveData, RxOrcData, RxXdfData or RxTextData data source. Can be NULL if a list of data source objects is provided for inData1.

inFile2

the second data set to merge; either a character string denoting the path to an existing .xdf file or an RxXdfData object.

outFile

in local compute context, an .xdf path to store the merged output. If the outFile already exists, overwrite must be set to TRUE to overwrite the file. If NULL, a data frame containing the merged data will be returned. In RxSpark compute context, an RxParquetData, RxHiveData, RxOrcData or RxXdfData data source.

matchVars

character vector containing the names of the variables to match for merging. In local compute context, the data sets MUST BE presorted in the same order by these variables, unless autoSort is set to TRUE. See rxSort. Not required for type equal to "union" or "oneToOne".

type

a character string defining the merge method to use:

  • "inner" compares each row of inData1 with each row of inData2 to find all pairs of rows in which the values of the matchVars are the same.
  • "oneToOne" appends columns from inData1 to inData2. Not supported in RxSpark compute context.
  • "left" includes all rows that match (as in "inner") plus rows from inData1 that no not have matches. NA's will be used for the values for variables from inData2 that are not matched.
  • "right" includes all rows that match (as in "inner") plus rows from inData2 that no not have matches. NA's will be used for the values for variables from inData1 that are not matched.
  • "full" is a combination of both "left" and "right" merge.
  • "union" append rows from inData2 to inData1. Not supported in RxSpark compute context. The two input files must have the same number of columns with the same data types.

missingsLow

a logical scalar for controlling the treatment of missing values. If TRUE, missing values in the data are treated as the lowest value; if FALSE, they are treated as the highest value. Not supported in RxSpark compute context.

autoSort

a logical scalar for controlling whether or not to sort the input data sets by the matchVars before merging. If TRUE, the data sets are sorted before merging; if FALSE, it is assumed that the data sets are already sorted by the matchVars. Not supported in RxSpark compute context.

duplicateVarExt

a character vector of length two containing the extensions to be used for handling duplicate variable names in the two input data sets. These extensions are not applied to matching variables. If NULL, file or data frame names will be used as the extension. If the names are the same, the extensions 1 and 2 will be used (unless there are other variables with those names.) For example, if duplicateVarExt = c("One", "Two") and inData1 and inData2 both have the variable y, the output data set will contain the variables y.One and y.Two.

varsToKeep1

character vector of variable names to include from the inData1. If NULL, argument is ignored. Cannot be used with varsToDrop1.

varsToDrop1

character vector of variable names to exclude from inData1. If NULL, argument is ignored. Cannot be used with varsToKeep1.

newVarNames1

a named character vector of new names for variables from inData1 when writing them to outData. For example, specifying c(x = "newx", y = "newy" would give the input variables x and y the names newx and newy in the output data.

varsToKeep2

character vector of variable names to include from the inData2. If NULL, argument is ignored. Cannot be used with varsToDrop2.

varsToDrop2

character vector of variable names to exclude from inData2. If NULL, argument is ignored. Cannot be used with varsToKeep2.

newVarNames2

a named character vector of new names for variables from inData2 when writing them to outData. For example, specifying c(x = "newx", y = "newy" would give the input variables x and y the names newx and newy in the output data.

rowsPerOutputBlock

an integer specifying how many rows should be written out to each block in the output .xdf file. If set to -1, the smaller of the two average block sizes of the input data sets will be used. Ignored if outData is NULL. Not supported in RxSpark compute context.

decreasing

a logical scalar specifying whether or not the matchVars variables were sorted in decreasing or increasing order. The input data must be sorted in the same order.

overwrite

logical value. If TRUE, an existing outFile will be overwritten. Ignored if outData is NULL

maxRowsByCols

the maximum size of a data frame that will be returned if outFile is set to NULL and inData is an .xdf file , measured by the number of rows times the number of columns. If the number of rows times the number of columns being created from the .xdf file exceeds this, a warning will be reported and the number of rows in the returned data frame will be truncated. If maxRowsByCols is set to be too large, you may experience problems from loading a huge data frame into memory. Not supported in RxSpark compute context.

bufferLimit

integer specifiying the maximum size of the memory buffer (in Mb) to use in merging. The default value of bufferLimit = -1 will attempt to determine an appropriate buffer limit based on system memory. Not supported in RxSpark compute context.

reportProgress

integer value with options:

  • 0: no progress is reported.
  • 1: the number of processed rows is printed and updated.
  • 2: rows processed and timings are reported.
  • 3: rows processed and all timings are reported. Not supported in RxSpark compute context.

verbose

integer value. If 0, no additional output is printed. If 1, additional summary information is printed.

xdfCompressionLevel

integer in the range of -1 to 9. The higher the value, the greater the amount of compression for the output file - resulting in smaller files but a longer time to create them. If xdfCompressionLevel is set to 0, there will be no compression and the output file will be compatible with the 6.0 release of Revolution R Enterprise. If set to -1, a default level of compression will be used.

...

additional arguments to be passed directly to the Microsoft R Server Compute Engine.

Details

The arguments varsToKeep1 (or alternatively varsToDrop1) and varsToKeep2 (or alternatively varsToDrop2) are used to define the set of variables from the input files that will be stored in the specified merged outFile file. The matchVars must be included in the variables read from the input files. A single copy of the matchVars variables will be saved in the outFile file.

Value

For rxMerge: If an outFile is not specified, a data frame with the merged data is returned. If an outFile is specified, a data source object is returned that can be used in subsequent RevoScaleR analysis. For rxMergeXdf: If merging is successful, TRUE is returned; otherwise FALSE is returned.

Author(s)

Microsoft Corporation Microsoft Technical Support

See Also

sort

Examples


 ###
 # Small data frame example
 ###

 x <- 1:20
 y <- 20:1
 df1 <- data.frame(x=x, y=y)

 x <- 20:1
 y <- 1:20
 df2 <- data.frame(x=x, y=y)

 # Merge the two data frames into an .xdf file, matching on the variable x
 outXDF <- file.path(tempdir(), ".rxTempOut.xdf")
 rxMerge(inData1 = df1, inData2 = df2, outFile=outXDF, matchVars = "x", overwrite=TRUE)

 # Read the data from the .xdf file into a data frame.  y.df1 and y.df2 should be the same
 df3 <- rxDataStep(inData = outXDF )
 df3

 if(file.exists(outXDF)) file.remove(outXDF)

 ###
 # Merge two data frames, matching y1 from the first with y2 from the second
 # Notice that the match variable is sorted in decreasing order.
 x1 <- 1:20
 y1 <- 20:1
 df1 <- data.frame(x1=x1, y1=y1)

 x2 <- 1:20
 y2 <- 25:6
 df2 <- data.frame(x2=x2, y2=y2)

 dfOut <- rxMerge(inData1 = df1, inData2 = df2, matchVars = "y2", decreasing=TRUE,
          newVarNames1 = c(y1 = "y2"))

 # Look at the resulting merged data 
 rxGetInfo( dfOut,numRows=10,getVarInfo=TRUE )

 # Merge an .xdf file and a data frame into a new .xdf file

 # .xdf file names
 indXDF <- file.path(tempdir(), ".rxTempIn.xdf")
 outXDF <- file.path(tempdir(), ".rxTempOut.xdf")

 indData <- data.frame(id = 1:12, state = rep(c("CA","OR", "WA"), times = 4))
 # Put individual-level data frame in .xdf file
 rxDataStep(inData = indData, outFile = indXDF, overwrite=TRUE)

 # Create state-level data frame
 stateData <- data.frame(state=c("CA","OR", "WA"), stateVal = c(1000, 400, 500))

 # Merge individual-level .xdf file with state-level data frame
 rxMerge(inData1 = indXDF, inData2 = stateData, outFile = outXDF,
     matchVars = "state")

 # Re-sort data by id
 rxSort(inData = outXDF, outFile = outXDF, sortByVars = "id", overwrite = TRUE)

 # Look at merged, sorted data
 df4 <- rxDataStep(inData = outXDF)
 df4