path.diagram in SEM--display covariances without variances

Dear Dustin,

-----Original Message-----
From: Dustin Fife [mailto:fife.dustin at gmail.com]
Sent: November-09-11 2:12 PM
To: John Fox
Cc: r-help at r-project.org
Subject: Re: [R] path.diagram in SEM--display covariances without
variances

Thanks for the quick response...I've never edited someone else's
package before. How do I go about doing that?

I wouldn't change the sem package, but rather create your own version of
pathDiagram(). You could examine the package sources, but, more simply, to
see the code for the function, type its name at the command prompt:

library(sem)

Loading required package: MASS
Loading required package: matrixcalc

pathDiagram

function (model, ...)
{
? ?UseMethod("pathDiagram")
}
<bytecode: 0000000006E1CEA8>
<environment: namespace:sem>

So pathDiagram() is a generic function. What methods are available?

methods(pathDiagram)

[1] pathDiagram.sem*

? Non-visible functions are asterisked

There is, therefore just one method, for objects of class "sem", hidden in
the sem namespace. To see it (most lines elided):

sem:::pathDiagram.sem

function (model, file, min.rank = NULL, max.rank = NULL, same.rank = NULL,
? ?variables = model$var.names, parameters = rownames(model$ram),
? ?ignore.double = TRUE, edge.labels = c("names", "values",
? ? ? ?"both"), size = c(8, 8), node.font = c("Helvetica", 14),
? ?edge.font = c("Helvetica", 10), rank.direction = c("LR",
? ? ? ?"TB"), digits = 2, standardize = FALSE, output.type = c("graphics",
? ? ? ?"dot"), graphics.fmt = "pdf", dot.options = NULL, ...)
{
. . .
? ?cat(file = handle, "}\n")
? ?if (output.type == "graphics" && !missing(file)) {
? ? ? ?cmd <- paste("dot -T", graphics.fmt, " -o ", graph.file,
? ? ? ? ? ?" ", dot.options, " ", dot.file, sep = "")
? ? ? ?cat("Running ", cmd, "\n")
? ? ? ?result <- try(system(cmd))
? ?}
? ?invisible(NULL)
}
<bytecode: 00000000071B9568>
<environment: namespace:sem>

Just copy the functions into an editor and make whatever changes you want.

Best,
?John

On Wed, Nov 9, 2011 at 12:47 PM, John Fox <jfox at mcmaster.ca> wrote:

Dear Dustin,

-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
project.org] On Behalf Of Dustin Fife
Sent: November-09-11 10:57 AM
To: r-help at r-project.org
Subject: [R] path.diagram in SEM--display covariances without
variances

Forgive me if I'm posting to the wrong place....It's my first time
posting.

Here's the situation: I'm using the sem package and making path
diagrams using path.diagrams. Suppose I have the following code:

. . .

The diagram is produces is hard to read because of the many

variances

that are shown. The covariance estimates are important for my
diagram, but the variances are not. Is there a way to suppress the
variance arrows without suppressing the covariance arrows?

No, but (1) pathDiagram() (the name of the function in the current
version of the sem package) produces an editable text file, from

which

you could remove the arrows that you don't want to see; and (2) you
could modify
pathDiagram() -- the code for the function is, after all, available

to

you
-- so that it does what you want.

I hope this helps,
?John

--------------------------------
John Fox
Senator William McMaster
?Professor of Social Statistics
Department of Sociology
McMaster University
Hamilton, Ontario, Canada
http://socserv.mcmaster.ca/jfox

--
Dustin Fife
Graduate Student, Quantitative Psychology University of Oklahoma

--
Dustin Fife
Fife Photography
www.fifephotography.com
info at fifephotography.com
fife.dustin at gmail.com
405.414.5599