Displaying 20 results from an estimated 6000 matches similar to: "Fit sem model with intercept"
2006 Jul 25
1
HELP with NLME
Hi,
I was very much hoping someone could help me with the following.
I am trying to convert some SAS NLMIXED code to NLME in R (v.2.1),
but I get an error message. Does anyone have any suggestions?
I think my error is with the random effect "u" which seems to be
parametrized differently in the SAS code. In case it's helpful,
what I am essentially trying to do is estimate parameters
2008 Nov 26
1
Request for Assistance in R with NonMem
Hi
I am having some problems running a covariate analysis with my
colleage using R with the NonMem program we are using for a graduate
school project. R and NonMem run fine without adding in the
covariates, but the program is giving us a problem when the covariate
analysis is added. We think the problem is with the R code to run the
covariate data analysis. We have the control stream, R code
2004 Feb 26
2
Structural Equation Model
Hello all!
I want to estimate parameters in a MIMIC model. I have one latent
variable (ksi), four reflexive indicators (y1, y2, y3 and y4) and four
formative indicators (x1, x2, x3, x4). Is there a way to do it in R? I
know there is the SEM library, but it seems not to be possible to
specify formative indicators, that is, observed exogenous variables
which causes the latent variable.
Thanks,
2009 Feb 02
1
Fit indexes in SEM with categorical data + ML estimation
Hello,
It has been found that SEM analysis using polychoric correlations + maximum
likelihood estimator produces incorrect test statistics and standard errors
(e.g., Flora, D. B., & Curran, P. J. (2004). An Empirical Evaluation of
Alternative Methods of Estimation for Con?rmatory Factor Analysis With
Ordinal Data. Psychological Methods, 9(4), 466-491).
Standard errors can be dealt with by
2002 Feb 11
0
profile
I am running 1.3.1 on a Windows (NT 4.0) machine. I've fit a nonlinear
model intended to predict crop yield from nutrient information, and want to
use the profile function. If I type say,
profile(simparj.fm)
I get the following error message:
"Error in prof$getProfile(): number of iterations exceeded maximum of
5.25515e-308"
I used the profiler function to profile simparj,fm step
2007 Jul 26
3
substituting dots in the names of the columns (sub, gsub, regexpr)
Dear R users,
I have the following two problems, related to the function sub, grep,
regexpr and similia.
The header of the file(s) I have to import is like this.
c("y (m)", "BD (g/cm3)", "PR (Mpa)", "Ks (m/s)", "SP g./g.", "P
(m3/m3)", "theta1 (g/g)", "theta2 (g/g)", "AWC (g/g)")
To get rid of spaces and
2007 Apr 09
1
Dealing with large nominal predictor in sem package
Hi,
I am using tsls function from sem package to estimate a model which includes large number of data. Among its predictors, it has a nominal data which has about 10 possible values. So I expand this parameter into 9-binary-value predictors with the coefficient of base value equals 0. I also have another continuous predictor.
The problem is that, whenever I run the tsls, I will get 'System
2009 May 20
1
sem with categorical data
I am trying to run a confirmatory factor analysis using the SEM package. My
data are ordinal. I have read
http://socserv.mcmaster.ca/jfox/Misc/sem/SEM-paper.pdf.
When I apply the hetcor function, I receive the following error:
Error in checkmvArgs(lower = lower, upper = upper, mean = mean, corr = corr,
:
at least one element of 'lower' is larger than 'upper'
Example:
2011 Mar 08
1
SEM error
Dear All,
I am new for R and SEM. I try to fit the model with Y (ordinal outcome), X
(4 categorical data), M1-M3 (continuous), and 2 covariates (Age&sex) as a
diagram.
library(polycor)
model.ly <-specify.model()
1: x -> m1, gam11, NA
2: x -> m2, gam12, NA
3: x -> m3, gam13, NA
4: age -> m1, gam14, NA
5: age -> m2, gam15, NA
6: age -> m3, gam16, NA
7: sex -> m1,
2005 Oct 10
1
SEM with dichotomous indicators
Hello,
I'd like to know if there is a way to fit a Structural equation model with
dichotomous indicators (ex: problem with a phone solved/ or not) having
effects on a ordinal variable.
How I do that using R?
Do you have an example with the code in R that you can send to me?
Thanks a lot!
Renata Estrella
UFRJ, Brasil, Rio de Janeiro
Renata Leite Estrella
Assistente de
2010 Jan 03
1
Questions regarding sem using hetcor() function from polycor and diagrams
Hello R Users,
While I have attempted to dig into the R help files and I have not
identified the answer to these questions, I apologize in advance if my
questions were answered in the past. I also recognize that one of my
questions unfortunately verges on statistical rather than code
territory. I have two rather unrelated questions about using the sem and
polycor packages for a relatively
2007 Aug 12
1
SEM for categorical data
Hi
I am looking for a structural equation modeling package in R which can be
used for categorical data. Is anyone aware of the existence of such a
package? Would appreciate any help on this.
Thank you
Upasna
--
---------------------------------------------------------------------
Upasna Sharma
Research Scholar
Shailesh J. Mehta School of Management,
Indian Institute of Technology, Bombay
2009 Apr 21
1
How to compare parameters of non linear fitting curves
Hi,
I'm using a non linear model to fit experimental survival curves.
This model describes the fraction of "still active" experiments as a
function of time t as follows:
f(t)=(1+exp(-etaD*cD)) / (1+exp(etaD(t-cD)))
Moreover, when experiments are still active, they may change of state
(from 0 to 1). But they may fall inactive before changing their state
(their state still
2013 Jan 23
2
CFA with lavaan or with SEM
Hi
Sorry for the rather long message.
I am trying to use the cfa command in the lavaan package to run a CFA however I am unsure over a couple of issues.
I have @25 dichotomous variables, 300 observations and an EFA on a training dataset suggests a 3 factor model.
After defining the model I use the command
fit.dat <- cfa(model.1, data=my.dat, std.lv = T, estimator="WLSMV",
2007 Apr 21
1
Fitting multinomial response in structural equation
Hi - I am confronting a situation where I have a set of structural equation and one or two of my responses are multinomial. I understand that sem would not deal with the unordered response. So I am thinking of the following two ways:
1. Expanding my response to a new set of binary variables corresponding to each label of my multinomial response. Then use each of these as a separate response in my
2008 May 29
1
appropriate covariance matrix for multiple nominal exogenous and multiple continuous endogenous variables in SEM
Hi,
I would like to use the sem package to perform a path analysis (no
latent variables) with a mixture of 2 nominal exogenous, 1 continuous
exogenous, and 4 continuous endogenous variables. I seek advice as to
how to calculate the appropriate covariance matrix for use with the sem
package.
I have read through the polycor package, and am confused as to the use
of "numeric" for
2008 Mar 15
1
again with polr
hello everybody
solved the problem with summary, now I have another one
eg I estimate
> try.op <- polr(
> as.ordered(sod.sit.ec.fam) ~
> log(y) +
> log(1 + nfiglimin) +
> log(1 + nfiglimagg) +
> log(ncomp - nfiglitot) +
> eta +
> I(eta^2) +
>
2011 Feb 14
4
sem problem - did not converge
Someone can help me? I tried several things and always don't converge
# Model
library(sem)
dados40.cov <- cov(dados40,method="spearman")
model.dados40 <- specify.model()
F1 -> Item11, lam11, NA
F1 -> Item31, lam31, NA
F1 -> Item36, lam36, NA
F1 -> Item54, lam54, NA
F1 -> Item63, lam63, NA
F1 -> Item65, lam55, NA
F1 -> Item67, lam67, NA
F1 ->
2012 Mar 23
0
Fixing error variance in a path analysis to model measurement error in scales using sem package
Hi!
I want to construct a path analysis model that can account for measurement
error in totally aggregated parcels, which refer to parcels where all of
the items in a scale are summed or averaged. If I am not mistaken, Bollen
(1989) advocates the following formula for computing the error variance of
each parcel:
(1−α(parcel))×variance(parcel),
such that α refers to Cronbach's alpha, which
2010 Feb 25
1
Heterogeneous Correlation Matrix with Survey Weights
Hello,
I have a data set containing categorical and ordinal factors, as well as
sampling weights (i.e., survey weights reflecting unequal probabilities of
selection). I want to fit a structural equation model with sem(). I have
run sem() on weighted covariance matrices using advice from John Fox (see
<http://tolstoy.newcastle.edu.au/R/e5/help/08/12/8773.html> and