ds.skewness {dsBaseClient}  R Documentation 
This function calculates the skewness of a numeric variable that is stored on the serverside (Opal server).
ds.skewness(x = NULL, method = 1, type = "both", datasources = NULL)
x 
a character string specifying the name of a numeric variable. 
method 
an integer value between 1 and 3 selecting one of the algorithms for computing skewness. For more information see Details. The default value is set to 1. 
type 
a character string which represents the type of analysis to carry out.

datasources 
a list of 
This function is similar to the function skewness
in R package e1071
.
The function calculates the skewness of an input variable x
with three different methods:
(1) If method
is set to 1 the following formula is used skewness= \frac{\sum_{i=1}^{N} (x_i  \bar(x))^3 /N}{(\sum_{i=1}^{N} ((x_i  \bar(x))^2) /N)^(3/2) }
,
where \bar{x}
is the mean of x and N
is the number of observations.
(2) If method
is set to 2
the following formula is used skewness= \frac{\sum_{i=1}^{N} (x_i  \bar(x))^3 /N}{(\sum_{i=1}^{N} ((x_i  \bar(x))^2) /N)^(3/2) } * \frac{\sqrt(N(N1)}{n2}
.
(3) If method
is set to 3 the following formula is used skewness= \frac{\sum_{i=1}^{N} (x_i  \bar(x))^3 /N}{(\sum_{i=1}^{N} ((x_i  \bar(x))^2) /N)^(3/2) } * (\frac{N1}{N})^(3/2)
.
The type
argument can be set as follows:
(1) If type
is set to 'combine'
, 'combined'
, 'combines'
or 'c'
,
the global skewness is returned.
(2) If type
is set to 'split'
, 'splits'
or 's'
,
the skewness is returned separately for each study.
(3) If type
is set to 'both'
or 'b'
, both sets of outputs are produced.
If x
contains any missing value, the function removes those before
the calculation of the skewness.
Server functions called: skewnessDS1
and skewnessDS2
ds.skewness
returns a matrix showing the skewness of the input numeric variable,
the number of valid observations and the validity message.
Demetris Avraam, for DataSHIELD Development Team
## 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()
connections < DSI::datashield.login(logins = logindata, assign = TRUE, symbol = "D")
#Calculate the skewness of LAB_TSC numeric variable for each study separately and combined
ds.skewness(x = "D$LAB_TSC",
method = 1,
type = "both",
datasources = connections)
# Clear the Datashield R sessions and logout
DSI::datashield.logout(connections)
## End(Not run)