Displaying 20 results from an estimated 3000 matches similar to: "Welch test for equality of variance"
2007 Feb 07
1
Problem with subsets and xyplot
Hello
I have a dataframe that looks like this
MSA CITY HIVEST YEAR YR CAT
1 0200 Albuquerque 0.50 1996 1996 5
2 0520 Atlanta 13.00 1997 1997 5
3 0720 Baltimore 29.10 1994 1994 1
4 0720 Baltimore 13.00 1995 1995 5
5 0720 Baltimore 3.68
2005 Sep 19
1
Use of least-squares means, are they misleading?
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Hi.
Sorry for sending this question twice, but I would really like to know
your opinion on this topic.
I have been reading about the (in)convenience of using least-squares
means (a. k. a. adjusted means) in multiple comparisons (I used to
resort to them when using SAS). I even read a post in this list warning
against them, but not giving much detail.
2005 Nov 10
2
Help to multinomial analyses
Dear Sirs,
Could you please be so kind as to send us some information on residuals in
multinomial logistic models? Is it possible to use R software?
We thank you in advance.
Sincerely yours
Luciana Alves,MSc
Beatriz Leimann, MD
--
Luciana Correia Alves
Doutoranda em Sa??de P??blica
ENSP - Fiocruz
2004 Jun 09
3
more obvious contribution mechanism?
can we put a "how to donate money to R" on the R webpage? perhaps with
a paypal button?
even better, because I would like to donate some funds from my research
budget, could the R-project possibly sell some trinkets for a high price
for support? it is difficult to explain to a non-profit org (like yale)
why i want to donate its money to another non-profit org. they would be
2004 Mar 03
7
Location of polr function
Hello
I am running R 1.8.1 on a Windows platform
I am attempting to fit an ordinal logistic regression model, using the
polr function, as described in Venables and Ripley. But when I try
model4 <- polr(ypsxcat~committed + as.factor(sex)
+ as.factor(drugusey) + anycsw + as.factor(sex)*committed
+ as.factor(sex)*as.factor(drugusey)+as.factor(sex)*anycsw, data =
duhray)
I get a message
2003 Jul 23
6
Condition indexes and variance inflation factors
Has anyone programmed condition indexes in R?
I know that there is a function for variance inflation factors
available in the car package; however, Belsley (1991) Conditioning
Diagnostics (Wiley) notes that there are several weaknesses of VIFs:
e.g. 1) High VIFs are sufficient but not necessary conditions for
collinearity 2) VIFs don't diagnose the number of collinearities and 3)
No one has
2003 Nov 08
2
Effects of rounding on regression
Does anyone know of research on the effects of rounding on regression?
e.g., when you ask people "How often have you _______?" you are more
likely to get answers like 100, 200, etc. than 98, 203, etc.
I'm interested in investigating this, but don't want to reinvent the
wheel.
thanks
Peter
Peter L. Flom, PhD
Assistant Director, Statistics and Data Analysis Core
Center for
2003 Sep 08
2
Yet another beginner question
Thanks for all the help on my earlier questions.....
How do you plot a simple time series with unequal intervals? I have
the following
dateofpoll <- as.ts(c("6/1/02", "7/1/02", "10/1/02", "1/4/03",
"1/25/03",
"6/7/03", "7/16/03", "8/17/03", "9/4/03"))
reelect <- c(51, 47, 49, 51, 49, 49, 46, 45, 40)
2004 Jun 21
2
Welch-JM-Test or Brown-Forsythe-Test in R?
Does oneway.test do what you want?
Hope this helps,
Matt Wiener
-----Original Message-----
From: r-help-bounces at stat.math.ethz.ch
[mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of Sven Hartenstein
Sent: Monday, June 21, 2004 3:23 PM
To: r-help at stat.math.ethz.ch
Subject: [R] Welch-JM-Test or Brown-Forsythe-Test in R?
Hi,
I want to test mean differences of > 2 groups with
2003 Sep 05
3
Dotchart question
Sorry to keep asking elementary questions......I appreciate the help.
I am trying to create a dotchart with the rows sorted according to the
values, rather than the labels. When I try
prof <- c('Accountant', 'Administrative assistant', 'Garment worker',
'Cook',
'Dentist', 'General practictioner', 'Graduate student', 'High level
2003 Oct 29
2
Where is rmutil package?
Pursing my earlier question, when I tried loading Lindsey's gnlm, I got
a
message
Loading required package: rmutil
Warning message:
There is no package called 'rmutil' in: library(package, character.only
= TRUE, logical = TRUE, warn.conflicts = warn.conflicts,
According to the R documentation
http://finzi.psych.upenn.edu/R/doc/html/packages.html
rmutil is in the standard
2005 Nov 04
1
Graphics question on putting axes in the margins
Hello
I am writing an article demonstrating how quantile plots work. In one
figure, I generate 3 sets of normal data, and add different sorts of
outliers to each. I then make 9 qqnorm plots, in a 3x3 array:
Outlier1 Outler2 Outlier3
Dataset1
Dataset2
Dataset3
which I did using mfrow = c(3,3).
I'd like to use the space on the page as efficiently as possible,so I
2005 Sep 27
5
graphics guide?
I am trying to create some graphs with R and it seems to be able to do
what I need. However, I have so far not been able to find any sort of
explanation of how the graphics system works. I am for instance trying
to create a multiple figure, and I seem to have to call plot.new()
before every new plot command, I have however not found any
explanation of what this actually does. ?plot.new does give
2003 Aug 26
2
Simple simulation in R
Hello all
I have a feeling this is very simple......but I am not sure how to do
it
My boss has two variables, one is an average of 4 numbers, the other is
an average of 3 of those numbers i.e
var1 = (X1 + X2 + X3 + X4)/4
var2 = (X1 + X2 + X3)/3
all of the X variables are supposed to be measuring similar constructs
not surprisingly, these are highly correlated (r = .98), the question
is how
2004 Jun 09
3
Dot chart question
Running R 1.8.1 on a Windows machine
In dotchart, I would like to shrink the labels on the tick marks (that
is, the numbers) without shrinking anything else. I could not find this
in either the Rhelp archives or in ?dotchart, which recmmends cex to
avoid 'label overlap', but cex shrinks all the characters in the plot.
Is there a way to do this?
Thanks
Peter
Peter L. Flom, PhD
2005 Mar 30
1
fastbw question
Hello
I am running R 2.0.1 on Windows, I am attempting to use Frank Harrell's
'fastbw' function (from the Design library), but I get an error that the
fit was not created with a Design library fitting function; yet when I
go to the help for fastbw (and also look in Frank's book Regression
Modeling Strategies) it appears that fastbw should work with a model
created with lm.....
2009 Dec 02
4
Finding cases in one subset that are closet to another subset
Good afternoon
Running R2.10.0 on Windows
I have a data frame that includes (among much else) a factor (In_2006) and a continuous variable (math_3_4). I would like to find the 2 cases for In_2006 = 0 that are closest to each case where In_2006 = 1.
My data looks like
In_2006 math_3_4
0 55.1
1 51.6
1 18.1
1 26.6
1 14.1
2004 Oct 08
1
polr and optim question
Hello again
I am trying to fit an ordinal logistic model using the polr function
from MASS. When I run
model.loan.ordinal <- polr(loancat~age + sex + racgp + yrseduc +
needlchg + gallery + sniffball + smokeball + sniffher +
smokeher + nicocaine + inject + poly(year.of.int,3) + druginj +
inj.years)
I get an error
Error in optim(start, fmin, gmin, method = "BFGS", hessian =
2003 Jul 15
1
Tree question
I was under the impression that the tree method (e.g. as implemented in
rpart) was insensitive to monotonic transformations of the dependent
variable. e.g. Breiman Olshen et al. Classification and Regression
Trees state "In a standard data structure [a tree] is invariant under
all monotone transformations of individual ordered varaibles" (p. 57)
However, I get very different results
2004 Oct 09
2
polr problem solved
I'd like to thank John Fox and Chuck Cleland for their help in resovling
this issue. It turned out to be something simple, but perhaps others
have had similar problems
In my original data frame, I had 4 categories of race/ethnicity. One of
the categories (other) was very small, and not similar to any of the
other three categories, so I created a new data frame deleting those
people.