Description Usage Arguments Details Value Author(s) See Also Examples
Displays a plot of the data and invites the user to “click” on points judged to lie on the various components.
1 2 
fmla 
A formula specifying the regression model to be fitted. 
data 
A list or data frame in which the variables specified by

ncomp 
Positive integer scalar. The number of components in the mixture which is to be fitted. 
eqVar 
Logical scalar; should the error variance be the same for all components? (The alternative is that each component should be allowed to have a different error variance.) 
chsnPts 
A list with 
keepPlotVisible 
Logical scalar. Should the plot of the data, produced by this
function, be kept visible after the model has been “fitted”?
(Rather than being dismissed by 
If the model involves more than one predictor, or if the specified predictor is a matrix with more than one column, then an error is thrown. This function is intended for use only with onevariable regression.
If there is an intercept in the model, then for each component
(numbered 1 to ncomp
) the user is invited to click
on two points judged to lie on a line underlying that
component. If there is no intercept, then the user is invited
to click on a single point for each component, with the origin
(0,0)
taken (silently) to be the second point needed to
determine the line.
The fit that this function returns is calculated by assigning a component to each point in the data set, based on which of the visually determined lines that point is closest to.
If eqVar
is TRUE
then the model is constructed using
a factor, whose entries are these assigned components, as a predictor
(along with the “x
” variable in fmla
) in a
call to lm()
. If code eqVar
is FALSE
then a
model is fitted separately to each component. (See the code for
details.) “Obviously” the linear coefficient estimates will
be the same in either case. Only the error variance estimates
will differ.
If eq.var
is TRUE
then the number of parameters in
the model, as used in the calculation of aic
, is M =
2*K + (K1) + 1 = 3*K
when there is an intercept term and M
= K + (K1) + 1 = 2*K
when there is no intercept term.
If eq.var
is FALSE
then the number of parameters
is M = 2*K + (K1) + K = 4*K  1
if there is an intercept,
and M = K + (K1) + K = 3*K  1
if there is no intercept.
The argument chsnPts
allows one to use this function
in a noninteractive session by creating and saving, a
priori, an object to be supplied as the value of chsnPts
.
If chsnPts
is supplied then the method employed isn't
really “visual”, but presumably the object supplied
would have been created in a visual manner. Be that as it may,
this function is mainly intended to be used visually, that is
without supplying chsnPts
.
If chsnPts
is not supplied then (“obviously”!!!) this
function can be used only in an interactive session.
An object of class "mixreg"
. (See mixreg()
.)
Components nsteps
and converged
are set to NA
.
Component data
has an extra column groups
appended
to it. This column is a factor specifying the components assigned
to the points on the basis of distances from the lines determined
by the chosen points.
The value also has an attribute "chsnPts"
. This is the
list of points judged by the user to lie on the component lines
(or the value of the chsnPts
argument if this was supplied).
Rolf Turner r.turner@auckland.ac.nz
1 2 3 4 5 6 7 8 9 10  ## Not run:
vfita < visualFit(plntsInf ~ aphRel,data=aphids,ncomp=2)
plot(vfita)
vfitk1 < visualFit(y ~ x, data=kilnAoneOut, ncomp=3)
cp < attr(vfitk1,"chsnPts")
vfitk2 < visualFit(y ~ x, data=kilnAoneOut, eqVar=TRUE, chsnPts=cp)
vfitk1$parmat
vfitk2$parmat # Same as above except for the "sigsq" column.
## End(Not run)

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