We acknowledge that many coding standards exist. A coding style is a coding preference, that should promote coding being read easily and code being maintainable. DataSHIELD developers should adopt a consistent coding style through the development of their packages. We welcome the following R coding styles:

Naming convention

DataSHIELD has two types of functions; client and server-side. Some constraints brought by the Opal Server adds some naming constraints.

Variable and argument names

It is strongly encouraged to use meaningful names for any variables and arguments. The name should be bring some contexts and indication of their purpose. So it is best to avoid using variable names using a single letters, such as ``a”, ``b”. It is best to avoid naming that can bring some confusion; i.e., ``var.1”, ``var.2”.

Client-side function convention

Each client-side function name starts with the three characters “ds.” before a function name. For example ds.assign or ds.mean. This naming convention differentiates the DataSHIELD functions with the R functions and other packages.

ds.[name of function] <- function()
{
}

Function arguments

For consistency, please, respect the following standard:

datasource argument is always last
newObj argument indicates a new variable is created on the server. It is a character variable set to “newObj”
x argument is a character variable that represents a server variable.

Server-side function convention

To accommodate the server-side function from the client, each server-side function name ends with the two characters ``DS”. For example, ``tableDS”, ``varDS”.

[name of function]DS <- function()
{
}

Documentation

Server-side and client-side functions must be documented using ROxygen 2. The documentation can be found here. Some examples are given below.

Client-side function documentation

We strongly encourage documentation to provide this level of details.

@title lists all objects on a server-side environment
#' @description creates a list of the names of all of the objects in
#' a specified serverside environment. 
#' @details When running analyses one may want to know the objects already generated. This 
#' request is not disclosive as it only returns the names of the objects and not their contents. 
#' 
#' By default, objects in DataSHIELD's Active Serverside Analytic Environment (\code{.GlobalEnv})
#' will be listed. This is the environment that contains all of the objects that server-side DataSHIELD 
#' is using for the main analysis or has written out to the server-side during the process
#' of managing or undertaking the analysis (variables, scalars, matrices, data frames, etc).
#'  
#' The environment to explore is specified by the argument \code{env.to.search} (i.e. environment
#' to search) to an integer value. The default environment 
#' which R names as \code{.GlobalEnv} is set by specifying \code{env.to.search = 1} or \code{1L}
#' (\code{1L} is just an explicit way of writing the integer \code{1}). 
#' 
#' If the \code{search.GlobalEnv} argument is set to TRUE the \code{env.to.search} parameter  
#' is set to \code{1L} regardless of what value it is set in the call
#' or if it is set to NULL. 
#' So, if \code{search.GlobalEnv} is set to TRUE, \code{ds.ls} will automatically
#' search the \code{.GlobalEnv} R environment on the server-side which contains all of the
#' variables, data frames and other objects read in at the start of the analysis,
#' as well as any new objects of any sort created using DataSHIELD assign functions. 
#' 
#' Other server-side environments contain other
#' objects. For example, environment \code{2L} contains the functions loaded via the native R
#' stats package and \code{6L} contains the standard list of datasets built into R. By default
#' \code{ds.ls} will return a list of ALL of the objects in the environment specified by the
#' \code{env.to.search} argument but you can specify search filters including \code{*} wildcards
#' using the \code{search.filter} argument.
#' 
#' In \code{search.filter} you can use the symbol \code{*} to find all the object that contains
#' the specified characters. For example, \code{search.filter = "Sd2*"} 
#' will list the names of all objects in the specified
#' environment with names beginning capital S, lower case d and number 2. 
#' Similarly, \code{search.filter="*.ID"} will return all objects with names ending with \code{.ID},
#' for example \code{Study.ID}. 
#' If a value is not specified for the \code{search.filter} argument or it is set as NULL, the names of 
#' all objects in the specified environment will be returned.
#' 
#' Server function called: \code{lsDS}. 
#' 
#' @param search.filter character string (potentially including \code{*} symbol) specifying the filter 
#' for the object name that you want to find in the enviroment. For more information see \strong{Details}. 
#' @param env.to.search an integer (e.g. in \code{2} or \code{2L} format) specifying the position
#' in the search path of the environment to be explored. \code{1L} is the current active analytic
#' environment on the server-side and is the default value of \code{env.to.search}.
#' For more information see \strong{Details}.
#' @param search.GlobalEnv Logical. If TRUE, \code{ds.ls} will list all objects
#' in the \code{.GlobalEnv} R environment on the server-side. If FALSE and if \code{env.to.search} is also
#' set as a valid integer, \code{ds.ls} will list all objects in the server-side R environment
#' identified by \code{env.to.search} in the search path. 
#' For more information see \strong{Details}.
#' @param datasources a list of \code{\link{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{datashield.connections_default}}.
#' @return \code{ds.ls} returns to the client-side a list containing: \cr
#' (1) the name/details of the server-side R environment which \code{ds.ls} has searched;\cr
#' (2) a vector of character strings giving the names of
#' all objects meeting the naming criteria specified by the argument \code{search.filter} in this
#' specified R server-side environment;\cr
#' (3) the nature of the search filter string as it was applied. 
#' @author DataSHIELD Development Team
#' @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()
#'   
#'   connections <- DSI::datashield.login(logins = logindata, assign = TRUE, symbol = "D") 
#'   
#'   #Example 1: Obtain the list of  all objects on a server-side environment
#'   
#'   ds.ls(datasources = connections)
#'   
#'   #Example 2: Obtain the list of all objects that contain "var" character in the name
#'   #Create in the server-side variables with "var" character in the name
#'   
#'   ds.assign(toAssign = "D$LAB_TSC",
#'             newobj = "var.LAB_TSC",
#'             datasources = connections)
#'   ds.assign(toAssign = "D$LAB_TRIG",
#'             newobj = "var.LAB_TRIG",
#'             datasources = connections)
#'   ds.assign(toAssign = "D$LAB_HDL",
#'             newobj = "var.LAB_HDL",
#'             datasources = connections)
#'   
#'   ds.ls(search.filter = "var*",
#'         env.to.search = 1L,
#'         search.GlobalEnv = TRUE,
#'         datasources = connections)
#'   
#'   # clear the Datashield R sessions and logout
#'   datashield.logout(connections)
#' }
#'
#' @export

Server-side function documentation