docData {umx}

Twin data for Direction of causation modelling

Description

A dataset containing indicators for two traits varA and varB, each measured in MZ and DZ twins.

Usage

data(docData)

Format

A data frame 6 manifests for each of two twins in 1400 families of MZ and DZ twins

Details

It is designed to show off umxDoC() testing the hypothesis varA causes varB, varB causes varA, both cause each other.

• zygosity "MZFF", "DZFF", "MZMM", or "DZMM"

• varA1_T1 Twin one's manifest 1 for varA

• varA2_T1 Twin one's manifest 2 for varA

• varA3_T1 Twin one's manifest 3 for varA

• varB1_T1 Twin one's manifest 1 for varB

• varB2_T1 Twin one's manifest 2 for varB

• varB3_T1 Twin one's manifest 3 for varB

• varA1_T2 Twin two's manifest 1 for varA

• varA2_T2 Twin two's manifest 2 for varA

• varA3_T2 Twin two's manifest 3 for varA

• varB1_T2 Twin two's manifest 1 for varB

• varB2_T2 Twin two's manifest 2 for varB

• varB3_T2 Twin two's manifest 3 for varB

References

• N.A. Gillespie and N.G. Martin (2005). Direction of Causation Models. In Encyclopedia of Statistics in Behavioral Science, 1, 496–499. Eds. Brian S. Everitt & David C. Howell

See Also

• umxDoC(), plot.MxModelDoC(), umxSummary.MxModelDoC(), umxModify()

Other datasets: Fischbein_wt, GFF, iqdat, umx, us_skinfold_data

Examples

data(docData)
str(docData)
mzData = subset(docData, zygosity %in% c("MZFF", "MZMM"))
dzData = subset(docData, zygosity %in% c("DZFF", "DZMM"))
par(mfrow = c(1, 2))  # 1 rows and 3 columns
plot(varA1_T2 ~varA1_T1, ylim = c(-4, 4), data = mzData, main="MZ")
tmp = round(cor.test(~varA1_T1 + varA1_T2, data = mzData)$estimate, 2)
text(x=-4, y=3, labels = paste0("r = ", tmp))
plot(varA1_T2 ~varA1_T1, ylim = c(-4, 4), data = dzData, main="DZ")
tmp = round(cor.test(~varA1_T1 + varA1_T2, data = dzData)$estimate, 2)
text(x=-4, y=3, labels = paste0("r = ", tmp))
par(mfrow = c(1, 1))  # back to as it was