Checks if a server-side object is valid

Checks if a vector or table structure has a number of observations equal to or greater than the threshold set by DataSHIELD.

ds.isValid(x = NULL, datasources = NULL)

Arguments

x

a character string specifying the name of a vector, dataframe or matrix.

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.

Value

ds.isValid returns a boolean. If it is TRUE input object is valid, FALSE otherwise.

Details

In DataSHIELD, analyses are possible only on valid objects to ensure the output is not disclosive. This function checks if an input object is valid. A vector is valid if the number of observations is equal to or greater than a set threshold. A factor vector is valid if all its levels (categories) have a count equal or greater than the set threshold. A data frame or a matrix is valid if the number of rows is equal or greater than the set threshold.

Server function called: isValidDS

Author

DataSHIELD Development Team

Examples

if (FALSE) {

  ## 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()
  
  connections <- DSI::datashield.login(logins = logindata, assign = TRUE, symbol = "D") 
  
  # Check if the dataframe assigned above is valid
  ds.isValid(x = 'D',
             datasources = connections) #all servers are used
  ds.isValid(x = 'D',
             datasources = connections[2]) #only the second server is used (study2)
 
  # clear the Datashield R sessions and logout
  datashield.logout(connections)

}