Extract parameter variance covariance matrix
Usage
# S4 method for class 'SingleGroupClass'
vcov(object)References
Chalmers, R., P. (2012). mirt: A Multidimensional Item Response Theory Package for the R Environment. Journal of Statistical Software, 48(6), 1-29. doi:10.18637/jss.v048.i06
Examples
# \donttest{
x <- mirt(Science, 1, SE=TRUE)
vcov(x)
#> a1.1 d1.2 d2.3 d3.4 a1.5
#> a1.1 0.0354557222 0.031747211 0.0218991330 -1.337062e-02 -0.0020114572
#> d1.2 0.0317472109 0.240747985 0.0496914145 -7.728604e-03 -0.0039962941
#> d2.3 0.0218991330 0.049691414 0.0495440979 -3.353138e-03 -0.0026118813
#> d3.4 -0.0133706166 -0.007728604 -0.0033531385 2.516506e-02 0.0016239413
#> a1.5 -0.0020114572 -0.003996294 -0.0026118813 1.623941e-03 0.0330717252
#> d1.6 -0.0027776758 0.000321554 0.0013455096 4.475090e-03 0.0222002454
#> d2.7 -0.0008339773 0.002234984 0.0026641307 3.634982e-03 0.0084726682
#> d3.8 0.0025280813 0.006109937 0.0050768040 2.151939e-03 -0.0194002583
#> a1.9 -0.0292529857 -0.032667514 -0.0224516013 1.338132e-02 0.0001401001
#> d1.10 -0.0438210135 -0.037345358 -0.0240181907 2.417470e-02 -0.0060425885
#> d2.11 -0.0206416044 -0.015080644 -0.0081996180 1.457986e-02 -0.0023410675
#> d3.12 0.0177727573 0.023980089 0.0183114800 -1.142724e-03 0.0022121845
#> a1.13 0.0096842437 0.008486325 0.0055838516 -3.358253e-03 -0.0026345430
#> d1.14 0.0070930997 0.010415451 0.0077963642 4.886259e-06 -0.0038164066
#> d2.15 0.0021935448 0.005091505 0.0044161993 2.013700e-03 -0.0013475415
#> d3.16 -0.0040629009 -0.001253710 0.0001366316 4.584220e-03 0.0020482028
#> d1.6 d2.7 d3.8 a1.9 d1.10
#> a1.1 -0.0027776758 -0.0008339773 0.002528081 -0.0292529857 -0.0438210135
#> d1.2 0.0003215540 0.0022349842 0.006109937 -0.0326675142 -0.0373453579
#> d2.3 0.0013455096 0.0026641307 0.005076804 -0.0224516013 -0.0240181907
#> d3.4 0.0044750896 0.0036349818 0.002151939 0.0133813229 0.0241746980
#> a1.5 0.0222002454 0.0084726682 -0.019400258 0.0001401001 -0.0060425885
#> d1.6 0.0572478298 0.0178719080 -0.008242431 -0.0042731331 0.0008943475
#> d2.7 0.0178719080 0.0204197987 0.001805256 -0.0022635445 0.0034073931
#> d3.8 -0.0082424309 0.0018052557 0.041235925 0.0021523979 0.0112367277
#> a1.9 -0.0042731331 -0.0022635445 0.002152398 0.2343596830 0.3068823433
#> d1.10 0.0008943475 0.0034073931 0.011236728 0.3068823433 0.5333187949
#> d2.11 0.0043839472 0.0058509494 0.008542531 0.1425287134 0.2140840706
#> d3.12 0.0095948178 0.0084870680 0.005845643 -0.1227407709 -0.1520698557
#> a1.13 -0.0031158076 -0.0007826477 0.003057944 -0.0316626320 -0.0478697496
#> d1.14 0.0007925371 0.0027067338 0.006134230 -0.0304997627 -0.0348586852
#> d2.15 0.0024475628 0.0032306664 0.004352544 -0.0097796669 -0.0072522805
#> d3.16 0.0048748828 0.0037848620 0.002008196 0.0177300358 0.0307235701
#> d2.11 d3.12 a1.13 d1.14 d2.15
#> a1.1 -0.0206416044 0.017772757 0.0096842437 7.093100e-03 0.0021935448
#> d1.2 -0.0150806437 0.023980089 0.0084863254 1.041545e-02 0.0050915045
#> d2.3 -0.0081996180 0.018311480 0.0055838516 7.796364e-03 0.0044161993
#> d3.4 0.0145798573 -0.001142724 -0.0033582533 4.886259e-06 0.0020137003
#> a1.5 -0.0023410675 0.002212184 -0.0026345430 -3.816407e-03 -0.0013475415
#> d1.6 0.0043839472 0.009594818 -0.0031158076 7.925371e-04 0.0024475628
#> d2.7 0.0058509494 0.008487068 -0.0007826477 2.706734e-03 0.0032306664
#> d3.8 0.0085425306 0.005845643 0.0030579443 6.134230e-03 0.0043525441
#> a1.9 0.1425287134 -0.122740771 -0.0316626320 -3.049976e-02 -0.0097796669
#> d1.10 0.2140840706 -0.152069856 -0.0478697496 -3.485869e-02 -0.0072522805
#> d2.11 0.1276826104 -0.062018021 -0.0219424374 -1.277452e-02 0.0003957921
#> d3.12 -0.0620180212 0.104233499 0.0192987094 2.313630e-02 0.0117967217
#> a1.13 -0.0219424374 0.019298709 0.0335900564 2.461211e-02 0.0088923418
#> d1.14 -0.0127745164 0.023136304 0.0246121055 7.645466e-02 0.0179733534
#> d2.15 0.0003957921 0.011796722 0.0088923418 1.797335e-02 0.0197363548
#> d3.16 0.0175005019 -0.003280364 -0.0143630948 -5.930600e-03 0.0028978863
#> d3.16
#> a1.1 -0.0040629009
#> d1.2 -0.0012537103
#> d2.3 0.0001366316
#> d3.4 0.0045842200
#> a1.5 0.0020482028
#> d1.6 0.0048748828
#> d2.7 0.0037848620
#> d3.8 0.0020081962
#> a1.9 0.0177300358
#> d1.10 0.0307235701
#> d2.11 0.0175005019
#> d3.12 -0.0032803641
#> a1.13 -0.0143630948
#> d1.14 -0.0059305999
#> d2.15 0.0028978863
#> d3.16 0.0284229583
# }