Displaying 20 results from an estimated 1000 matches similar to: "stepAIC/lme problem (1.7.0 only)"
2012 Oct 14
1
Problems with coxph and survfit in a stratified model, with interactions
First, here is your message as it appears on R-help.
On 10/14/2012 05:00 AM, r-help-request@r-project.org wrote:
> I?m trying to set up proportional hazard model that is stratified with
> respect to covariate 1 and has an interaction between covariate 1 and
> another variable, covariate 2. Both variables are categorical. In the
> following, I try to illustrate the two problems that
2012 Jul 06
2
Anova Type II and Contrasts
the study design of the data I have to analyse is simple. There is 1 control group (CTRL) and 2 different treatment groups (TREAT_1 and TREAT_2).
The data also includes 2 covariates COV1 and COV2. I have been asked to check if there is a linear or quadratic treatment effect in the data.
I created a dummy data set to explain my situation:
df1 <- data.frame(
Observation =
2008 Aug 18
1
lmer syntax, matrix of (grouped) covariates?
I have a fairly large model:
> length(Y)
[1] 3051
> dim(covariates)
[1] 3051 211
All of these 211 covariates need to be nested hierarchically within a
grouping "class", of which there are 8. I have an accessory vector, "
cov2class" that specifies the mapping between covariates and the 8 classes.
Now, I understand I can break all this information up into individual
2010 Jan 30
2
Questions on Mahalanobis Distance
Hello,
I am a new R user and trying to learn how to implement the mahalanobis
function to measure the distance between to 2 population centroids. I
have used STATISTICA to calculate these differences, but was hoping to learn
to do the analysis in R. I have implemented the code as below, but my
results are very different from that of STATISTICA, and I believe I may not
have interpreted the help
2006 Jul 11
2
Multiple tests on 2 way-ANOVA
Dear r-helpers,
I have a question about multiple testing.
Here an example that puzzles me:
All matrixes and contrast vectors are presented in treatment contrasts.
1. example:
library(multcomp)
n<-60; sigma<-20
# n = sample size per group
# sigma standard deviation of the residuals
cov1 <- matrix(c(3/4,-1/2,-1/2,-1/2,1,0,-1/2,0,1), nrow = 3, ncol=3, byrow=TRUE,
dimnames =
2009 Aug 02
1
Competing Risks Regression with qualitative predictor with more than 2 categories
Hello,
I have a question regarding competing risk regression using cmprsk package (function crr()). I am using R2.9.1. How can I do to assess the effect of qualitative predictor (gg) with more than two categories (a,b,c) categorie c is the reference category. See above results, gg is considered like a ordered predictor !
Thank you for your help
Jan
> # simulated data to test
> set.seed(10)
2012 Oct 13
4
Problems with coxph and survfit in a stratified model with interactions
I?m trying to set up proportional hazard model that is stratified with
respect to covariate 1 and has an interaction between covariate 1 and
another variable, covariate 2. Both variables are categorical. In the
following, I try to illustrate the two problems that I?ve encountered, using
the lung dataset.
The first problem is the warning:
To me, it seems that there are too many dummies
2013 Oct 18
1
crr question in library(cmprsk)
Hi all
I do not understand why I am getting the following error message. Can
anybody help me with this? Thanks in advance.
install.packages("cmprsk")
library(cmprsk)
result1 <-crr(ftime, fstatus, cov1, failcode=1, cencode=0 )
one.pout1 = predict(result1,cov1,X=cbind(1,one.z1,one.z2))
predict.crr(result1,cov1,X=cbind(1,one.z1,one.z2))
Error: could not find function
2002 Dec 04
1
Mixture of Multivariate Gaussian Sample Data
Hey, I am confused about how to generate the sample data from a mixture of
Multivariate Gaussian ditribution.
For example, there are 2 component Gaussian with prior
probability of 0.4 and 0.6,
the means and variances are
u1=[1 1]', Cov1=[1 0;0 1]
and
u2=[-1 -1]', Cov2=[1 0;0 1]
repectively.
So how can I generate a sample of 500 data from the above mixture
distribution?
Thanks.
Fred
2009 May 22
0
EM algorithm mixture of multivariate
Hi, i would to know, if someone have ever write the code to estimate the
parameter (mixing proportion, mean, a var/cov matrix) of a mixture of two
multivariate normal distribution. I wrote it and it works (it could find
mean and mixing proportion, if I fix the var/cov matrix), while if I fix
anything, it doesn't work. My suspect is that when the algorithm iterates
the var/cov matrix, something
2009 May 22
0
EM algorithm mixture of multivariate gaussian
Hi, i would to know, if someone have ever write the code to estimate the
parameter (mixing proportion, mean, a var/cov matrix) of a mixture of two
multivariate normal distribution. I wrote it and it works (it could find
mean and mixing proportion, if I fix the var/cov matrix), while if I fix
anything, it doesn't work. My suspect is that when the algorithm iterates
the var/cov matrix, something
2017 Jun 08
1
stepAIC() that can use new extractAIC() function implementing AICc
I would like test AICc as a criteria for model selection for a glm using
stepAIC() from MASS package.
Based on various information available in WEB, stepAIC() use
extractAIC() to get the criteria used for model selection.
I have created a new extractAIC() function (and extractAIC.glm() and
extractAIC.lm() ones) that use a new parameter criteria that can be AIC,
BIC or AICc.
It works as
2005 Aug 15
2
stepAIC invalid scope argument
I am trying to replicate the first example from stepAIC from the MASS
package with my own dataset but am running into error. If someone can
point where I have gone wrong, I would appreciate it very much.
Here is an example :
set.seed(1)
df <- data.frame( x1=rnorm(1000), x2=rnorm(1000), x3=rnorm(1000) )
df$y <- 0.5*df$x1 + rnorm(1000, mean=8, sd=0.5)
# pairs(df); head(df)
lo <-
2011 Mar 19
1
strange PREDICTIONS from a PIECEWISE LINEAR (mixed) MODEL
Hi Dears,
When I introduce an interaciton in a piecewise model I obtain some quite
unusual results.
If that would't take u such a problem I'd really appreciate an advise from
you.
I've reproduced an example below...
Many thanks
x<-rnorm(1000)
y<-exp(-x)+rnorm(1000)
plot(x,y)
abline(v=-1,col=2,lty=2)
mod<-lm(y~x+x*(x>-1))
summary(mod)
yy<-predict(mod)
2013 Nov 25
4
lmer specification for random effects: contradictory reults
Hi All,
I was wondering if someone could help me to solve this issue with lmer.
In order to understand the best mixed effects model to fit my data, I
compared the following options according to the procedures specified in many
papers (i.e. Baayen
<http://www.google.it/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CDsQFjAA
2012 Jul 30
1
te( ) interactions and AIC model selection with GAM
Hello R users,
I'm working with a time-series of several years and to analyze it, I?m using
GAM smoothers from the package mgcv. I?m constructing models where
zooplankton biomass (bm) is the dependent variable and the continuous
explanatory variables are:
-time in Julian days (t), to creat a long-term linear trend
-Julian days of the year (t_year) to create an annual cycle
- Mean temperature
2003 Feb 10
2
problems using lqs()
Dear List-members,
I found a strange behaviour in the lqs function.
Suppose I have the following data:
y <- c(7.6, 7.7, 4.3, 5.9, 5.0, 6.5, 8.3, 8.2, 13.2, 12.6, 10.4, 10.8,
13.1, 12.3, 10.4, 10.5, 7.7, 9.5, 12.0, 12.6, 13.6, 14.1, 13.5, 11.5,
12.0, 13.0, 14.1, 15.1)
x1 <- c(8.2, 7.6,, 4.6, 4.3, 5.9, 5.0, 6.5, 8.3, 10.1, 13.2, 12.6, 10.4,
10.8, 13.1, 13.3, 10.4, 10.5, 7.7, 10.0, 12.0,
2011 Apr 07
1
Automated Fixed Order Stepwise Regression Function
Greetings,
I am interested in creating a stepwise fixed order regression function. There's a function for this already called add1( ). The F statistics are calculated using type 2 anova (the SS and the F changes don't match SPSS's). You can see my use of this at the very end of the email.
What I want: a function to make an anova table with f changes and delt R^2.
I ran into
2010 Jan 29
2
Vectors with equal sd but different slope
Hi,
what I would need are 2 vector pairs (x,y) and (x1,y1). x and x1 must have
the same sd. y and y1 should also exhibit the same sd's but different ones
as x and x1. Plotting x,y and x1,y1 should produce a plot with 2 vectors
having a different slope. Plotting both vector pairs in one plot with fixed
axes should reveal the different slope.
many thanks
syrvn
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2004 Oct 31
3
strange results with dmvnorm
I am experiencing strange results using dmvnorm. I define a scaled distance
matrix from the coordinates bellow and then calculate a covariance matrix using
a spherical correlation function. Then with certain combinations of
range and sill parameters dmvnorm is returning values greater than 1. Surely
the results of dmvnorm should be in the interval 0:1 (or do I just nead a
holiday?). In addition