This vignette shows how to estimate interaction models, with both continuous and ordered (categorical) data.

Model Syntax

m <- '
  X =~ x1 + x2 + x3
  Z =~ z1 + z2 + z3
  Y =~ y1 + y2 + y3

  Y ~ X + Z + X:Z
'

Continuous Indicators

fit_cont <- pls(
  m,
  data      = modsem::oneInt,
  bootstrap = TRUE,
  boot.R    = 50
)
summary(fit_cont)
#> plssem (0.1.4) ended normally after 3 iterations
#>   Estimator                                       PLSc
#>   Link                                          LINEAR
#>                                                       
#>   Number of observations                          2000
#>   Number of iterations                               3
#>   Number of latent variables                         3
#>   Number of observed variables                       9
#> 
#> Fit Measures:
#>   Chi-Square                                    56.757
#>   Degrees of Freedom                                24
#>   SRMR                                           0.006
#>   RMSEA                                          0.026
#> 
#> R-squared (indicators):
#>   x1                                             0.863
#>   x2                                             0.819
#>   x3                                             0.809
#>   z1                                             0.830
#>   z2                                             0.827
#>   z3                                             0.843
#>   y1                                             0.934
#>   y2                                             0.919
#>   y3                                             0.923
#> 
#> R-squared (latents):
#>   Y                                              0.604
#> 
#> Latent Variables:
#>                  Estimate  Std.Error  z.value  P(>|z|)
#>   X =~          
#>     x1              0.929      0.012   75.834    0.000
#>     x2              0.905      0.015   61.806    0.000
#>     x3              0.899      0.013   70.530    0.000
#>   Z =~          
#>     z1              0.911      0.011   79.973    0.000
#>     z2              0.909      0.015   61.911    0.000
#>     z3              0.918      0.012   77.681    0.000
#>   Y =~          
#>     y1              0.966      0.006  174.278    0.000
#>     y2              0.959      0.008  116.493    0.000
#>     y3              0.961      0.006  147.962    0.000
#> 
#> Regressions:
#>                  Estimate  Std.Error  z.value  P(>|z|)
#>   Y ~           
#>     X               0.423      0.020   21.233    0.000
#>     Z               0.361      0.017   21.096    0.000
#>     X:Z             0.452      0.017   27.255    0.000
#> 
#> Covariances:
#>                  Estimate  Std.Error  z.value  P(>|z|)
#>   X ~~          
#>     Z               0.201      0.023    8.869    0.000
#>     X:Z             0.018      0.040    0.455    0.649
#>   Z ~~          
#>     X:Z             0.060      0.048    1.267    0.205
#> 
#> Variances:
#>                  Estimate  Std.Error  z.value  P(>|z|)
#>     X               1.000      0.022   45.244    0.000
#>     Z               1.000      0.033   30.396    0.000
#>    .Y               0.396      0.017   23.234    0.000
#>     X:Z             1.013      0.061   16.594    0.000
#>    .x1              0.137      0.023    6.034    0.000
#>    .x2              0.181      0.026    6.834    0.000
#>    .x3              0.191      0.023    8.333    0.000
#>    .z1              0.170      0.021    8.181    0.000
#>    .z2              0.173      0.027    6.493    0.000
#>    .z3              0.157      0.022    7.226    0.000
#>    .y1              0.066      0.011    6.167    0.000
#>    .y2              0.081      0.016    5.157    0.000
#>    .y3              0.077      0.012    6.201    0.000

Ordered Indicators

fit_ord <- pls(
  m,
  data      = oneIntOrdered,
  bootstrap = TRUE,
  boot.R    = 50,
  ordered   = colnames(oneIntOrdered) # explicitly specify variables as ordered
)
summary(fit_ord)
#> plssem (0.1.4) ended normally after 53 iterations
#>   Estimator                                  MCOrdPLSc
#>   Link                                          PROBIT
#>                                                       
#>   Number of observations                          2000
#>   Number of iterations                              53
#>   Number of latent variables                         3
#>   Number of observed variables                       9
#> 
#> Fit Measures:
#>   Chi-Square                                    20.432
#>   Degrees of Freedom                                24
#>   SRMR                                           0.012
#>   RMSEA                                          0.000
#> 
#> R-squared (indicators):
#>   x1                                             0.866
#>   x2                                             0.809
#>   x3                                             0.819
#>   z1                                             0.876
#>   z2                                             0.812
#>   z3                                             0.828
#>   y1                                             0.944
#>   y2                                             0.907
#>   y3                                             0.925
#> 
#> R-squared (latents):
#>   Y                                              0.568
#> 
#> Latent Variables:
#>                  Estimate  Std.Error  z.value  P(>|z|)
#>   X =~          
#>     x1              0.931      0.008  116.136    0.000
#>     x2              0.899      0.006  144.117    0.000
#>     x3              0.905      0.008  120.085    0.000
#>   Z =~          
#>     z1              0.936      0.007  131.513    0.000
#>     z2              0.901      0.009  103.157    0.000
#>     z3              0.910      0.009  102.644    0.000
#>   Y =~          
#>     y1              0.971      0.004  225.121    0.000
#>     y2              0.952      0.005  199.980    0.000
#>     y3              0.962      0.005  192.142    0.000
#> 
#> Regressions:
#>                  Estimate  Std.Error  z.value  P(>|z|)
#>   Y ~           
#>     X               0.418      0.020   20.766    0.000
#>     Z               0.356      0.019   18.923    0.000
#>     X:Z             0.447      0.019   23.042    0.000
#> 
#> Covariances:
#>                  Estimate  Std.Error  z.value  P(>|z|)
#>   X ~~          
#>     Z               0.195      0.022    8.916    0.000
#>     X:Z             0.003                             
#>   Z ~~          
#>     X:Z             0.008                             
#> 
#> Thresholds:
#>                  Estimate  Std.Error  z.value  P(>|z|)
#>     x1|t1          -2.147      0.102  -20.948    0.000
#>     x1|t2          -0.830      0.028  -29.652    0.000
#>     x1|t3           0.075      0.022    3.464    0.001
#>     x1|t4           0.898      0.036   24.872    0.000
#>     x1|t5           1.871      0.050   37.199    0.000
#>     x2|t1          -2.555      0.065  -39.115    0.000
#>     x2|t2          -1.570      0.046  -34.084    0.000
#>     x2|t3          -0.420      0.025  -16.820    0.000
#>     x2|t4           0.412      0.033   12.539    0.000
#>     x2|t5           1.307      0.050   26.383    0.000
#>     x2|t6           2.548      0.071   35.905    0.000
#>     x3|t1          -2.370      0.064  -36.961    0.000
#>     x3|t2          -1.253      0.037  -33.441    0.000
#>     x3|t3          -0.087      0.023   -3.806    0.000
#>     x3|t4           0.747      0.034   22.126    0.000
#>     x3|t5           2.107      0.081   26.090    0.000
#>     x3|t6           2.782      0.060   46.580    0.000
#>     y1|t1          -2.832      0.062  -45.690    0.000
#>     y1|t2          -1.496      0.054  -27.484    0.000
#>     y1|t3          -0.678      0.023  -29.927    0.000
#>     y1|t4           0.498      0.033   14.954    0.000
#>     y1|t5           1.597      0.054   29.506    0.000
#>     y1|t6           2.592      0.129   20.169    0.000
#>     y2|t1          -2.997      0.108  -27.679    0.000
#>     y2|t2          -1.653      0.051  -32.513    0.000
#>     y2|t3          -0.990      0.029  -34.172    0.000
#>     y2|t4           0.294      0.033    8.864    0.000
#>     y2|t5           1.068      0.052   20.456    0.000
#>     y2|t6           2.319      0.106   21.940    0.000
#>     y3|t1          -1.664      0.062  -26.803    0.000
#>     y3|t2          -0.849      0.023  -37.494    0.000
#>     y3|t3           0.309      0.031   10.086    0.000
#>     y3|t4           1.344      0.048   28.292    0.000
#>     y3|t5           2.204      0.092   23.993    0.000
#>     z1|t1          -2.040      0.075  -27.134    0.000
#>     z1|t2          -0.776      0.031  -25.224    0.000
#>     z1|t3           0.283      0.026   10.865    0.000
#>     z1|t4           0.938      0.031   30.387    0.000
#>     z1|t5           2.296      0.117   19.565    0.000
#>     z1|t6           3.316      0.053   62.302    0.000
#>     z2|t1          -2.894      0.054  -53.196    0.000
#>     z2|t2          -1.610      0.046  -35.287    0.000
#>     z2|t3          -0.742      0.032  -23.285    0.000
#>     z2|t4           0.245      0.028    8.893    0.000
#>     z2|t5           1.211      0.033   36.748    0.000
#>     z2|t6           2.317      0.125   18.551    0.000
#>     z3|t1          -3.343      0.074  -45.090    0.000
#>     z3|t2          -1.970      0.072  -27.187    0.000
#>     z3|t3          -1.281      0.046  -28.160    0.000
#>     z3|t4          -0.205      0.028   -7.279    0.000
#>     z3|t5           0.999      0.026   37.923    0.000
#>     z3|t6           1.661      0.050   33.350    0.000
#> 
#> Variances:
#>                  Estimate  Std.Error  z.value  P(>|z|)
#>     X               1.000                             
#>     Z               1.000                             
#>    .Y               0.432      0.031   14.098    0.000
#>     X:Z             1.033                             
#>    .x1              0.134      0.015    8.978    0.000
#>    .x2              0.191      0.011   17.028    0.000
#>    .x3              0.181      0.014   13.241    0.000
#>    .z1              0.124      0.013    9.342    0.000
#>    .z2              0.188      0.016   11.932    0.000
#>    .z3              0.172      0.016   10.627    0.000
#>    .y1              0.056      0.008    6.707    0.000
#>    .y2              0.093      0.009   10.279    0.000
#>    .y3              0.075      0.010    7.752    0.000