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rxGetInfo: Get Data Source Information

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Description

Get basic information about an RevoScaleR data source or data frame

Usage


  rxGetInfo(data, getVarInfo = FALSE, getBlockSizes = FALSE,
            getValueLabels = NULL, varsToKeep = NULL, varsToDrop = NULL,
            startRow = 1, numRows = 0, computeInfo = FALSE,
            allNodes = TRUE, verbose = 0)

Arguments

data

a data frame, a character string specifying an .xdf, or an RxDataSource object. If a local compute context is being used, this argument may also be a list of data sources, in which case the output will be returned in a named list. See the details section for more information.

getVarInfo

logical value. If TRUE, variable information is returned.

getBlockSizes

logical value. If TRUE, block sizes are returned in the output for an .xdf file, and when printed the first 10 block sizes are shown.

getValueLabels

logical value. If TRUE and getVarInfo is TRUE or NULL, factor value labels are included in the output.

varsToKeep

character vector of variable names for which information is returned. If NULL or getVarInfo is FALSE, argument is ignored. Cannot be used with varsToDrop.

varsToDrop

character vector of variable names for which information is not returned. If NULL or getVarInfo is FALSE, argument is ignored. Cannot be used with varsToKeep.

startRow

starting row for retrieval of data if a data frame or .xdf file.

numRows

number of rows of data to retrieve if a data frame or .xdf file.

computeInfo

logical value. If TRUE, and getVarInfo is TRUE, variable information (e.g., high/low values) for non-xdf data sources will be computed by reading through the data set. If TRUE, and getVarInfo is FALSE, the number of variables will be gotten from from non-xdf data sources (but not the number of rows).

allNodes

logical value. Ignored if the active RxComputeContext compute context is local or RxForeachDoPar. Otherwise, if TRUE, a list containing the information for the data set on each node in the active compute context will be returned. If FALSE, only information on the data set on the master node will be returned. Note that the determination of the master node is not controlled by the end user. See the RevoScaleR Distributed Computing Guide for more information on master node computations.

verbose

integer value. If 0, no additional output is printed. If 1, additional summary information is printed for an .xdf file.

Details

If a local compute context is being used, the data and file arguments may be a list of data source objects, e.g., data = list(iris, airquality, attitude), in which case a named list of results are returned. For rxGetInfo, a mix of supported data sources is allowed. Note that data frames should not be specified in quotes because, in that case, they will be interpreted as .xdf data paths.

If the RxComputeContext is distributed, rxGetInfo will request information from the compute context nodes.

Value

list containing the following possible elements:

fileName

character string containing the file name and path (if an .xdf file).

objName

character string containing object name (if not an .xdf file).

class

class of the object if an R object.

length

length of the object if it is not an .xdf file or data frame.

numCompositeFiles

number of composite data files(if a composite .xdf file).

numRows

number of rows in the data set.

numVars

number of variables in the data set.

numBlocks

number of blocks in the data set.

varInfo

list of variable information where each element is a list describing a variable. (See return value of rxGetVarInfo for more information.)

rowsPerBlock

integer vector containing number of rows in each block (if getBlockSizes is set to TRUE). Set to NULL if data is a data frame.

data

data frame containing the data (if numRows > 0)

If using a distributed compute context with the allNodes set to TRUE, a list of lists with information on the data from each node will be returned.

Author(s)

Microsoft Corporation Microsoft Technical Support

See Also

rxDataStep, rxGetVarInfo, rxSetVarInfo.

Examples


 # Summary information about a data frame
 fileInfo <- rxGetInfo(data = iris, numRows = 5)
 fileInfo

 # Summary information about an .xdf file
 mortFile <- file.path(rxGetOption("sampleDataDir"), "CensusWorkers")
 infoObj <- rxGetInfo(mortFile, getBlockSizes=TRUE)
 numBlocks <- infoObj$numBlocks
 aveRowsPerBlock <- infoObj$numRows/numBlocks
 rowsPerBlock <- infoObj$rowsPerBlock
 aveRowsPerBlock1 <- mean(rowsPerBlock)

 # Obtain information on a variety of data sources
 fourthGradersXDF <- file.path(rxGetOption("sampleDataDir"), "fourthgraders.xdf")
 KyphosisDS <- RxXdfData(file.path(rxGetOption("sampleDataDir"), "kyphosis.xdf"))
 claimsTxtDS <- RxTextData(file.path(rxGetOption("sampleDataDir"), "claims.txt"))
 rxGetInfo(data = list(iris, fourthGradersXDF, KyphosisDS, claimsTxtDS))