Displaying 3 results from an estimated 3 matches for "theta_j".
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2006 Mar 27
2
Clustering question \ dist(datmat)
Hello everybody. I am trying to cluster circular data (data points which are angles), thus i can not use the "dist" function in "mclust" to generate my distance matrix, I am using the function " Dij = 0.5*( 1 - cos(theta_i - theta_j)). The thing is "hclust" will not accept this distance matrix, i tried to put it in a data frame, but again i get an error message saying " Error in if (n < 2) stop("must have n >= 2 objects to cluster") : argument is of length zero". The distance matrix "di...
2004 Jun 06
0
strata() in clogit()
...log odds associated with the levels in strata()
within a clogit() model? I'm running R-1.9.0 on a Linux platform.
I am using clogit() to run a Rasch model in Item Response Theory in
psychometrics. Symbolically, the model is:
logit(p_{j,k}) = \log({\Pr(p_{j,k}) \over \Pr(1-p_{j,k})}) =
\theta_j - \alpha_k,
That is, the log odds of answering an test item correctly is a function
of the item difficulty (\theta_j) and the ability of individual
students (\alpha_k). The following R syntax gives me the \theta
coefficients associated with items i5 to i17, but summary() does not
automatically su...
2010 Oct 15
0
nomianl response model
Is there a way to estimate a nominal response model?
To be more specific let's say I want to calibrate:
\pi_{v}(\theta_j)=\frac{e^{\xi_{v}+\lambda_{v}\theta_j}}{\sum_{h=1}^m
e^{\xi_{h}+\lambda_{h}\theta_j}}
Where $\theta_j$ is a the dependent variable and I need to estimate
$\xi_{h}$ and $\lambda_{h}$ for $h \in {1...,m}$.
Thank you,
Mauricio Romero
Quantil S.A.S.
Cel: 3112231150
www.quantil.com.co
"It is...