iqdat: Twin data: IQ measured longitudinally across 4 ages.

In umx: Structural Equation Modeling and Twin Modeling in R

Twin data: IQ measured longitudinally across 4 ages.

Description

Measures of IQ across four ages in 261 pairs of identical twins and 301 pairs of fraternal (DZ) twins. (see details). It is used as data for the umxSimplex() examples.

Usage

data(iqdat)

Format

A data frame with 562 rows (twin families). Nine measures on each twin.

Details

• zygosity Zygosity (MZ or DZ)

• IQ_age1_T1 T1 IQ measured at age 1

• IQ_age2_T1 T1 IQ measured at age 2

• IQ_age3_T1 T1 IQ measured at age 3

• IQ_age4_T1 T1 IQ measured at age 4

• IQ_age1_T2 T2 IQ measured at age 1

• IQ_age2_T2 T2 IQ measured at age 2

• IQ_age3_T2 T2 IQ measured at age 3

• IQ_age4_T2 T2 IQ measured at age 4

References

Boomsma, D. I., Martin, N. G., & Molenaar, P. C. (1989). Factor and simplex models for repeated measures: application to two psychomotor measures of alcohol sensitivity in twins. Behavior Genetics, 19, 79-96. \Sexpr[results=rd]{tools:::Rd_expr_doi("10.1007/BF01065885")}.

See Also

umxSimplex()

Other datasets: Anthro_LDSC, Fischbein_wt, GFF, HSwls, Psych_LDSC, docData, umx, us_skinfold_data

Examples

## Not run: 
data(iqdat)
str(iqdat)
par(mfrow = c(1, 3))  # 1 rows and 3 columns
plot(IQ_age4_T1 ~ IQ_age4_T2, ylim = c(50, 150), data = subset(iqdat, zygosity == "MZ"))
plot(IQ_age4_T1 ~ IQ_age4_T2, ylim = c(50, 150), data = subset(iqdat, zygosity == "DZ"))
plot(IQ_age1_T1 ~ IQ_age4_T2, data = subset(iqdat, zygosity == "MZ"))
par(mfrow = c(1, 1))  # back to as it was

## End(Not run)

umx documentation built on Oct. 11, 2026, 5:07 p.m.