Running examples in 'sirt-Ex.R' failed
The error most likely occurred in:

> ### Name: f1d.irt
> ### Title: Functional Unidimensional Item Response Model
> ### Aliases: f1d.irt
> 
> ### ** Examples
> 
> #############################################################################
> # EXAMPLE 1: Dataset Mathematics data.math | Exploratory multidimensional model
> #############################################################################
> data(data.math)
> dat <- ( data.math$data )[, -c(1,2) ] # select Mathematics items
> 
> #****
> # Model 1: Functional unidimensional model based on original data
> 
> #++ (1) estimate model with 3 factors
> mod1 <- sirt::f1d.irt( dat=dat, nfactors=3)
*** Estimate tetrachoric correlation
Iteration 1 | Approximation error = 0.27408 | Max. parameter change = 4.68309
Iteration 2 | Approximation error = 0.22335 | Max. parameter change = 1.27014
Iteration 3 | Approximation error = 0.22003 | Max. parameter change = 0.30784
Iteration 4 | Approximation error = 0.21984 | Max. parameter change = 0.07312
Iteration 5 | Approximation error = 0.21983 | Max. parameter change = 0.01753
Iteration 6 | Approximation error = 0.21983 | Max. parameter change = 0.00422
Iteration 7 | Approximation error = 0.21983 | Max. parameter change = 0.00101
Iteration 8 | Approximation error = 0.21983 | Max. parameter change = 0.00024
Iteration 9 | Approximation error = 0.21983 | Max. parameter change = 6e-05
Iteration 10 | Approximation error = 0.21983 | Max. parameter change = 1e-05
Iteration 11 | Approximation error = 0.21983 | Max. parameter change = 0
> 
> #++ (2) plot results
>      par(mfrow=c(1,2))
> # Intercepts
> plot( mod1$item$di0, mod1$item$di.ast, pch=16, main="Item Intercepts",
+         xlab=expression( paste( d[i], " (Unidimensional Model)" )),
+         ylab=expression( paste( d[i], " (Functional Unidimensional Model)" )))
> abline( lm(mod1$item$di.ast ~ mod1$item$di0), col=2, lty=2 )
> # Discriminations
> plot( mod1$item$ai0, mod1$item$ai.ast, pch=16, main="Item Discriminations",
+         xlab=expression( paste( a[i], " (Unidimensional Model)" )),
+         ylab=expression( paste( a[i], " (Functional Unidimensional Model)" )))
> abline( lm(mod1$item$ai.ast ~ mod1$item$ai0), col=2, lty=2 )
>      par(mfrow=c(1,1))
> 
> #++ (3) estimate bifactor model and Green-Yang reliability
> gy1 <- sirt::greenyang.reliability( mod1$tetra, nfactors=3 )
Reliability Estimation Based on a Nonlinear SEM

Green & Yang (2009, Psychometrika). Reliability of summed item scores
  using structural equation modeling: An alternative to coefficient alpha

Omega_h for 1 factor is not meaningful, just omega_t
Warning in schmid(m, nfactors, fm, digits, rotate = rotate, n.obs = n.obs,  :
  Omega_h and Omega_asymptotic are not meaningful with one factor
Error in nchar(tv[1, 21]) : 'nchar()' requires a character vector
Calls: <Anonymous> ... <Anonymous> -> omegah -> omega.diagram -> multi.arrow
Execution halted