SignaltoNoiseRatio Plots
Description
A SignaltoNoiseRatio plot is created for designs of type taguchiDesign with at least two replicates.
Usage
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Arguments
object 
needs to be an object of class 
type 
character variable setting the type of the signaltonoiseratio plot. The following three can be chosen:
By default 
factors 
for which factor is the effectPlot to be created. 
fun 
a function for the construction of the effectPlot such as 
response 
response variable. If the response data frame of fdo consists of more then one responses, 
single 
logical value. If ‘TRUE’ device region can be set up using for instance 
points 
logical value. If ‘TRUE’ points are shown in addition to values out of 
classic 
logical value. ‘TRUE’ creates an effectPlot as depicted in most textbooks. 
axes 
logical value indicating wheter the axes should be drawn or not. 
lty 
numerical value which specifies the line type used. 
xlab 
a title for the x axis: 
ylab 
a title for the y axis: 
main 
an overall title for the plot: see 
ylim 
vector giving the range of the yaxis. 
... 
Arguments to be passed to methods, such as graphical parameters (see 
Details
snPlot
uses effectPlot
and creates an effect plot for the signaltonoise ratios as target values.
Depending on the used type
the target values for the single replications of the taguchi design will be calculated in the following way:

“nominal”: SN = 10*log(mean(y)/var(y))

“smaller”: SN = 10*log((1/n)*sum(y^2))

“larger”: SN = 10*log((1/n)*sum(1/y^2))
SignaltoNoise ratio plots are an additional tool to estimate the effects of the single factors. Beside the effect plot, which is used to identify the factor with the most effect to a process or something like that, the signaltonoise ratio plot can be used to judge the variance an d therefore the validity of the results of an effect plot.
Value
snPlot invisibly returns a data.frame containing all the single SignaltoNoise ratios.
Author(s)
Thomas Roth thomas.roth@tuberlin.de
Etienne Stockhausen stocdarf@mailbox.tuberlin.de
References
APTE, P.R.: Taguchi Method for Dynamic Problems  3 Day Taguchi Method Workshop at Unimap. Bombay, 2012.
See Also
interactionPlot
paretoPlot
facDesign
response
normalPlot
http://www.rqualitytools.org/html/Improve.html
Examples
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