plotProbe error (Latent moderation analysis and plot)

[Bo WANG]

Thanks in advance for any help!!!

I was conducting latent moderation analysis and want to plot the results with plotProbe function from the semTools package with the following code:

study2 <- spss.get("sample 2.sav",use.value.labels=TRUE)


moderationsample2 <- indProd(study2,var1 = c("x1","x2","x3","x4"),
                             var2 = c("m1","m2","m3","m4"), match = F,
                             meanC = T)

ModelSample2 <- '
XX =~ x1 + x2 + x3 
MM =~ m1 + m2 + m3
YY =~ y1 + y2 + y3 + y4 

INT =~ x1.m1 + x1.m2 + x1.m3 + x2.m1 + x2.m2 + x2.m3 + x3.m1 + x3.m2 + x3.m3 

XX ~~ 0*INT

MM ~~ 0*INT

YY ~ a*XX + b*MM + INT

x1 + m1 + y1 + x1.m1 ~ 0*1

XX + MM + YY + INT ~ NA*1

'

FitSample2 <- sem(ModelSample2, data = moderationsample2, std.lv = T, estimator = "MLR")

summary(FitSample2, fit = T, standardized = T, rsquare = T)

PlotSample2 <- probe2WayRC(FitSample2, nameX = c("XX", "MM", "INT"), nameY = "YY",
            modVar = "MM", valProbe = c(-1, 0, 1))

plotProbe(PlotSample2, xlim = c(-2, 2))

But it gave a warning message as follows after probe2WayRC function :

Warning messages:
1: In sqrt(varIntcept) : NaNs produced
2: In sqrt(varIntcept) : NaNs produced
3: In sqrt(varSlope) : NaNs produced
4: In sqrt(varSlope) : NaNs produced

So that the final graph looks like this:

[Terrence Jorgensen]

plotProbe(PlotSample2, xlim = c(-2, 2))

You are not fixing the latent mean to 0, so check the distribution of XX to make sure these values are not extrapolations.

lavInspect(FitSample2, "mean.ov")

lavInspect(FitSample2, "cov.ov") # sqrt(diag()) gives the SDs

Also, what does the PlotSample2 output look like?

Terrence D. Jorgensen

Assistant Professor, Methods and Statistics

Research Institute for Child Development and Education, the University of Amsterdam

http://www.uva.nl/profile/t.d.jorgensen