These functions are run for the side effects. There is no meaningful
return value.
Details
These functions will generate a sample of data and plot the
untrasformed data (left panels) and the transformed data (right
panels). Initially the value of lambda is 1 and the 2 sets of
plots will be identical.
You then adjust the transformation parameter lambda to see how
the right panels change.
The function vis.boxcox shows the effect of transforming the
y-variable in a simple linear regression.
The function vis.boxcoxu shows a single variable compared to
the normal distribution.
References
GEP Box; DR Cox. An Analysis of Transformations. Journal
of the Royal Statitical Society. Series B, Vol. 26, No. 2 (1964) 211-252