ds.changeRefGroup {dsBaseClient}

R Documentation

Changes the reference level of a factor in the server-side

Description

Change the reference level of a factor, by putting the reference group first.

This function is similar to R function relevel.

Usage

ds.changeRefGroup(
  x = NULL,
  ref = NULL,
  newobj = NULL,
  reorderByRef = FALSE,
  datasources = NULL
)

Arguments

x	a character string providing the name of the input vector of type factor.
ref	the reference level.
newobj	a character string that provides the name for the output object that is stored on the server-side. Default changerefgroup.newobj.
reorderByRef	logical, if TRUE the new vector should be ordered by the reference group (i.e. putting the reference group first). The default is to not re-order (see the reasons in the details).
datasources	a list of DSConnection-class objects obtained after login. If the datasources argument is not specified the default set of connections will be used: see datashield.connections_default.

Details

This function allows the user to re-order the vector, putting the reference group first. It should be mentioned that by default the reference is the first level in the vector of levels. If the user chooses the re-order a warning is issued as this can introduce a mismatch of values if the vector is put back into a table that is not reordered in the same way. Such mismatch can render the results of operations on that table invalid.

Server function called: changeRefGroupDS

Value

ds.changeRefGroup returns a new vector with the specified level as a reference which is written to the server-side.

Author(s)

DataSHIELD Development Team

See Also

ds.cbind Combines objects column-wise.

ds.levels to obtain the levels (categories) of a vector of type factor.

ds.colnames to obtain the column names of a matrix or a data frame

ds.asMatrix to coerce an object into a matrix type.

ds.dim to obtain the dimensions of a matrix or a data frame.

Examples

## Not run: 

  ## Version 6, for version 5 see the Wiki
  # Connecting to the Opal servers

  require('DSI')
  require('DSOpal')
  require('dsBaseClient')

  builder <- DSI::newDSLoginBuilder()
  builder$append(server = "study1", 
                 url = "http://192.168.56.100:8080/", 
                 user = "administrator", password = "datashield_test&", 
                 table = "CNSIM.CNSIM1", driver = "OpalDriver")
  builder$append(server = "study2", 
                 url = "http://192.168.56.100:8080/", 
                 user = "administrator", password = "datashield_test&", 
                 table = "CNSIM.CNSIM2", driver = "OpalDriver")
  builder$append(server = "study3",
                 url = "http://192.168.56.100:8080/", 
                 user = "administrator", password = "datashield_test&", 
                 table = "CNSIM.CNSIM3", driver = "OpalDriver")
  logindata <- builder$build()
  
  # Log onto the remote Opal training servers
  connections <- DSI::datashield.login(logins = logindata, assign = TRUE, symbol = "D") 

  # Changing the reference group in the server-side
 
    # Example 1: rename the categories and change the reference with re-ordering
      # print out the levels of the initial vector
      ds.levels(x= "D$PM_BMI_CATEGORICAL",
                datasources = connections)

      # define a vector with the new levels and recode the initial levels
      newNames <- c("normal", "overweight", "obesity")
      ds.recodeLevels(x = "D$PM_BMI_CATEGORICAL",
                      newCategories = newNames,
                      newobj = "bmi_new",
                      datasources = connections)

      # print out the levels of the new vector
      ds.levels(x = "bmi_new",
                datasources = connections)

      # Set the reference to "obesity" without changing the order (default)
      ds.changeRefGroup(x = "bmi_new",
                        ref = "obesity",
                        newobj = "bmi_ob",
                        datasources = connections)

      # print out the levels; the first listed level (i.e. the reference) is now 'obesity'
      ds.levels(x = "bmi_ob",
                datasources = connections)

    # Example 2: change the reference and re-order by the reference level
      # If re-ordering is sought, the action is completed but a warning is issued
      ds.recodeLevels(x = "D$PM_BMI_CATEGORICAL",
                      newCategories = newNames,
                      newobj = "bmi_new",
                     datasources = connections)
      ds.changeRefGroup(x = "bmi_new",
                        ref = "obesity",
                        newobj = "bmi_ob",
                        reorderByRef = TRUE,
                        datasources = connections)

           
  # Clear the Datashield R sessions and logout
  datashield.logout(connections) 

## End(Not run)

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