ds.cov: Computes covariance between two or more vectors
In datashield/dsStatsClient: DataSHIELD client site stattistical functions

Description Usage Arguments Details Value Author(s) Examples

This is similar to the R base function 'cov'.

1 2	ds.cov(x = NULL, y = NULL, naAction = "pairwise.complete.obs", datasources = NULL)

`datasources`	a list of opal object(s) obtained after login in to opal servers; these objects hold also the data assign to R, as `dataframe`, from opal datasources.
`x`	a character, the name of a numerical vector, matrix or dataframe
`y`	NULL (default) or the name of avector, matrix or data frame with compatible dimensions to x.
`naAction`	a character string giving a method for computing covariances in the presence of missing values. This must be one of the strings: "everything", "all.obs", "complete.obs", "na.or.complete", or "pairwise.complete.obs". The default value is set to "pairwise.complete.obs"

In addition to computing covariances; this function, unlike the R base function 'cov', produces a table outlining the number of complete cases to allow for the user to make a decision about the 'relevance' of the covariance based on the number of complete cases included in the covariance calculations.

a list containing the results of the test

GAYE, A.

{

  # load that contains the login details
  data(logindata)

  # login and assign specific variable(s)
  # (by default the assigned dataset is a dataframe named 'D')
  myvar <- list('LAB_HDL', 'LAB_TSC', 'GENDER')
  opals <- datashield.login(logins=logindata,assign=TRUE,variables=myvar)

  # Example 1: generate the covariance matrix for the assigned dataset 'D'
  # which contains 4 vectors (2 continuous and 1 categorical)
  ds.cov(x='D')

  # Example 2: calculate the covariance between two vectors
  # (first assign the vectors from 'D')
  ds.assign(newobj='labhdl', toAssign='D$LAB_HDL')
  ds.assign(newobj='labtsc', toAssign='D$LAB_TSC')
  ds.assign(newobj='gender', toAssign='D$GENDER')
  ds.cov(x='labhdl', y='labtsc')
  ds.cov(x='labhdl', y='gender')

  # clear the Datashield R sessions and logout
  datashield.logout(opals)

}