search for: polytom

Hi there, Does anyone know a method to calculate the number of different patterns in a given data frame. The variables are of polytomous type and not binary (for the latter i found a package called "countpattern" which unfortunately only functions for binary variables). V1 V2 V3 0 3 1 1 2 0 1 2 0 So, in this case, i would like to get "2" as output. Thanks in advance J?rgen

...43 .001 4 65 .05 67 0.001 v2... Is there a convenient way to plot the results? (I'd like to display visually the effects of the predictors: any sugestion?) OK, I probably miss something here (no experience with (non ordinal) polytomous logistic regression yet!) Thank very much to all Anne ---------------------------------------------------- Anne Piotet Tel: +41 79 359 83 32 (mobile) Email: anne.piotet@m-td.com --------------------------------------------------- M-TD Modelling and Technology Development PSE-C CH-1015 Lausan...

Hi all I have a dataset whose response is a categorical variable of the ordinal scale type (6 levels). I'm interested in building classification models, and I'm wondering if there is something implemented in R (or its packages) that I'm not aware of, to treat the ordinal scale measurements straightforwardly. I can think of the alternative of building a conditional (hierarchical)

I am new to generalized linear models and studying McCullagh & Nelder (1989). Especially, I have a problem resembling the \"cheese taste\" example (5.3.1. p. 109) of the book. I tried to analyse the cheese example with R but failed to do so because R allowed me to use logit link function only with binary family that supposes 0 <= y <= 1. Do I need to scale the y\'s or

Hello, Would someone have ever heard or developed any Item Response Models library for R ? Of course, a Rasch model can be estimated through glm() but it is not the case for more complex (polytomous) response models. Similarly I would be interested in any R implementation of nonlinear multivariate analyses a la GIFI (HOMALS, PRINCALS, OVERALS). Thanks a lot in advance, Yvonnick Noel, PhD. U. of Lille 3 Dpt. of Psychology F-59653 Villeneuve d'Ascq Cedex -.-.-.-.-.-.-.-.-.-.-.-.-.-.-....

...em response theory (IRT) likelihood that I want to maximize w.r.t. to theta (student ability). L(\theta) = \prod(p(x)) Where p(x) is the 3-parameter logistic model when items are scored dichotomously (x_{ij} = 0 or 1) and p(x) is Muraki's generalized partial credit model when items are scored polytomously (x_{ij} = 0 \ldots J). Now, I wrote the following two functions to maximize the likelihood. The first one is for the 3PL and works when all items are scored dichotmously. The second is for the GPCM and gives the MLE when all items are scored polytomously. In the code below, this requires tha...

Hello list, Is there any mean to fit models for ordinal response other than multinomial polytomous ("multinom" from nnet ) and cumulative logit ("polr" from MASS)? I am particularly interested in continuation-ratio model and adjacent-category logit model. It is for the sake of epidemiology in wild-living populations! Many thanks, Emmanuelle Fromont *****************...

...he occurence of an event (factor) having more than 2 levels with several continuous predictors. The model being ordinal, I was waiting the glm function to return several intercepts, which is not the case when looking to my results (I only have one intercept). I finally managed to perform an ordinal polytomous logisitc regression with the polr function, which gives several intercepts. But does anyone know what was the model performed with glm and why only one intercept was given ? Thanks a lot for your help ! -- View this message in context: http://r.789695.n4.nabble.com/glm-prediction-of-a-factor-w...

Dear R-users, I'd like to announce the release of the new version of package 'ltm' for analyzing multivariate dichotomous and polytomous data under the Item Response Theory approach. New features: * function tpm() (along with supporting methods, i.e., anova, plot, margins, factor.scores, etc.) has been added for fitting Birnbaum's Three Parameter Model. * grm() can now handle mix of dichotomous and polytomous items. *...

...been uploaded to CRAN. The package has been updated to include the following: 1) The irt.ability() function that estimates examinee ability given a set of item parameters. The function is very general and can be used to estimate ability when there are only dichotomous items (1-, 2-, or 3PL), only polytomous items (generalized partial credit model), or a mixture of dichotomous and polytomous items. The function can be used to estimate maximum likelihood estimates or two bayesian estimates: the maximum a posteriori (MAP) and the expected a posteriori (EAP). 2) The plaus.val() function that uses reje...

Dear R-users, I'd like to announce the release of the new version of package 'ltm' (i.e., ltm_0.9-0 soon available from CRAN) for Item Response Theory analyses. This package provides a flexible framework for analyzing dichotomous and polytomous data under various IRT models. Furthermore, supporting functions for descriptive statistics, goodness-of-fit, ability estimation and plotting are available. New features include: * function gpcm() (along with supporting methods, for the generic functions, anova, plot, margins, factor.scor...

Dear R-users I am introducing my collegue to R and she is interested to use R to perform Polytomous Logistic Regression called also Multi-category logistic regression. Is there any program in R doing this? Thank you so much for any feedback. I take this opportunity to thank people who were kind to answer my query about how to include a postscript file generated from R, in a latex file and...

Dear R-users, I'd like to announce the release of the new version of package 'ltm' for analyzing multivariate dichotomous and polytomous data under the Item Response Theory approach. New features: * function tpm() (along with supporting methods, i.e., anova, plot, margins, factor.scores, etc.) has been added for fitting Birnbaum's Three Parameter Model. * grm() can now handle mix of dichotomous and polytomous items. *...

...been uploaded to CRAN. The package has been updated to include the following: 1) The irt.ability() function that estimates examinee ability given a set of item parameters. The function is very general and can be used to estimate ability when there are only dichotomous items (1-, 2-, or 3PL), only polytomous items (generalized partial credit model), or a mixture of dichotomous and polytomous items. The function can be used to estimate maximum likelihood estimates or two bayesian estimates: the maximum a posteriori (MAP) and the expected a posteriori (EAP). 2) The plaus.val() function that uses reje...

Dear R-users, I'd like to announce the release of the new version of package 'ltm' (i.e., ltm_0.9-0 soon available from CRAN) for Item Response Theory analyses. This package provides a flexible framework for analyzing dichotomous and polytomous data under various IRT models. Furthermore, supporting functions for descriptive statistics, goodness-of-fit, ability estimation and plotting are available. New features include: * function gpcm() (along with supporting methods, for the generic functions, anova, plot, margins, factor.scor...

Hi everyone: Polyclass is a polytomous logistic regression model using linear splines and their tensor products. It provides estimates for conditional class probabilities which can then be used to predict class labels. I know there is Polyclass package in S-plus. So I'm wondering if there is a corresponding package in R? I have b...

A revised version of the MiscPsycho package has been uploaded to CRAN. The fixes include: 1) A bug found in the class.acc() function that resulted in overflow errors when computing probabilities associated with polytomously scored items has been resolved. The function now integrates over the posterior distribution of an IRT model for dichotomously scored items, polytomously scored items, or a combination of the two. 2) The help page for the irt.ability() function was updated. There was previously an error indica...

Hi, Can one tell me which procedure will fit an ordinal logistic regression model for longitudinal data set. To be precise, I have both dichotomous and polytomous items. Also, I would like to specify different covariance structures (unstructured, ar1 etc) for trial runs. Thanks -- View this message in context: http://www.nabble.com/ordinal-logistic-regression-for-longitudinal-data-set-tp23225097p23225097.html Sent from the R help mailing list archive a...

Hi all, I'm working on a multinomial (or "polytomous") logistic regression using R and have made great progress using multinom() from the nnet library. My response variable has three categories, and there are two different possible predictors. I'd like to use the likelihoods of certain models (ie, saturated, fitteds, and null) to ca...

...of the package plink has been uploaded to CRAN. plink is a package for conducting unidimensional IRT scaling and chain linking for multiple groups for single-format or mixed-format common items. The package supports eight IRT models and four calibration methods. Dichotomous Models: 1PL, 2PL, 3PL Polytomous Models: -Graded response model -Partial credit model -Generalized partial credit model -Nominal response model -Multiple-choice model Calibration Methods: -Mean/Mean -Mean/Sigma -Haebara -Stocking-Lord Any combination of dichotomous and polytomous items can be supplied with intermingled unique...