I am using your excellent R package eRM to solve a questionaire survey data. I meet a strange issue when using RSM function. This RSM runs well using sample data.
There is a test data like this: 'data.frame': 1669 obs. of 7 variables: $ X1: num 2 2 3 3 2 3 4 4 3 2 ... $ X2: num 4 3 3 2 3 4 4 4 3 3 ... $ X3: num 4 3 3 4 3 3 4 4 3 0 ... $ X4: num 2 3 2 4 1 2 3 3 3 1 ... $ X5: num 4 4 3 3 3 4 4 4 3 3 ... $ X6: num 4 4 4 3 3 4 4 4 3 3 ... $ X7: num 4 2 3 4 3 3 4 4 3 3 ... ### RSM(test) Warning in sqrt(diag(solve(parest$hessian))) : NaNs produced Warning in sqrt(diag(lres$W %*% solve(parest$hessian) %*% t(lres$W))) : NaNs produced Results of RSM estimation: Call: RSM(X = test) Conditional log-likelihood: 13768080 Number of iterations: 5 Number of parameters: 9 Item (Category) Difficulty Parameters (eta): X2 X3 X4 X5 X6 X7 Cat 2 Cat 3 Cat 4 Estimate -700.9534 -456.4338 901.4649 -1322.033 -1256.828 -673.2412 -231.5791 -3979.953 1911.748203 Std.Err NaN NaN NaN NaN NaN NaN NaN NaN 1.036215 ### So, I use a shortened data, run like this: RSM(test[1:283,]) Results of RSM estimation: Call: RSM(X = test[1:283, ]) Conditional log-likelihood: -1015.388 Number of iterations: 29 Number of parameters: 9 Item (Category) Difficulty Parameters (eta): X2 X3 X4 X5 X6 X7 Cat 2 Cat 3 Cat 4 Estimate -0.0739008 0.05655997 1.2203061 -1.1212188 -0.7547957 -0.0378593 1.2020940 3.2657449 8.501760 Std.Err 0.1018267 0.10026033 0.1003035 0.1195827 0.1125677 0.1013739 0.4387487 0.8161754 1.226057 ### However, when I add one record, from 283 to 284, RSM(test[1:284,]) Warning in sqrt(diag(solve(parest$hessian))) : NaNs produced Warning in sqrt(diag(lres$W %*% solve(parest$hessian) %*% t(lres$W))) : NaNs produced Results of RSM estimation: Call: RSM(X = test[1:284, ]) Conditional log-likelihood: 3369344 Number of iterations: 6 Number of parameters: 9 Item (Category) Difficulty Parameters (eta): X2 X3 X4 X5 X6 X7 Cat 2 Cat 3 Cat 4 Estimate -670.9137 -554.6215 527.789997 -1359.721 -1127.137 -626.1859 -126.7199 -4753.367 2134.408482 Std.Err 2152.9823 1679.2875 2.377241 NaN NaN 3394.5180 562.6800 11045.935 3.526018 I can’t find any special values in the data list X1 X2 X3 X4 X5 X6 X7 270 4 4 4 3 4 4 4 271 3 3 3 1 3 3 3 272 4 3 4 1 4 4 4 273 3 3 3 3 3 3 3 274 3 3 4 4 3 3 4 275 3 3 3 3 3 3 3 276 1 3 3 3 3 3 3 277 3 3 3 2 4 4 4 278 2 3 2 1 3 3 3 279 3 3 3 2 3 3 3 280 3 3 2 2 3 3 3 281 3 4 4 3 4 3 3 282 2 2 2 2 2 2 2 283 3 4 3 1 4 3 3 284 2 4 2 1 4 3 2 285 3 3 3 3 3 3 3 286 4 4 3 4 4 4 4 287 4 3 4 0 3 4 4 288 0 3 4 0 4 4 1 289 4 4 4 4 4 4 4 290 3 3 3 3 3 3 2 If I input many different numbers of data, the results often become strange. The data is appended at the letter. No na values in all data. Great thanks #### all data is in the appended file ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.