ds.colnames.Rd

% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/ds.colnames.R
\name{ds.colnames}
\alias{ds.colnames}
\title{Produces column names of the R object in the server-side}
\usage{
ds.colnames(x = NULL, datasources = NULL)
}
\arguments{
\item{x}{a character string providing the name of the input data frame or matrix.}

\item{datasources}{a list of \code{\link[DSI]{DSConnection-class}} objects obtained after login.
If the \code{datasources} argument is not specified
the default set of connections will be used: see \code{\link[DSI]{datashield.connections_default}}.}
}
\value{
\code{ds.colnames} returns the column names of
the specified server-side data frame or matrix.
}
\description{
Retrieves column names of an R object on the server-side.
This function is similar to R function \code{colnames}.
}
\details{
The input is restricted to the object of type \code{data.frame} or \code{matrix}.

Server function called: \code{colnamesDS}
}
\examples{
\dontrun{

  ## 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")

  # Getting column names of the R objects stored in the server-side
  ds.colnames(x = "D",
              datasources = connections[1]) #only the first server ("study1") is used
  # Clear the Datashield R sessions and logout
  datashield.logout(connections)
}
}
\seealso{
\code{\link{ds.dim}} to obtain the dimensions of a matrix or a data frame.
}
\author{
DataSHIELD Development Team
}