sortDat: Sort data by order of increasing survival time
In mesudell/joineRmeta: Joint Modelling for Meta-Analytic (Multi-Study) Data

This function is used internally in jointmeta1. It takes longitudinal and survival datasets, and orders them by increasing survival time.

1	sortDat(longdat, survdat, longdat2, survdat2)

`longdat`	longitudinal dataset with factor variables and interaction terms expanded out
`survdat`	survival dataset with factor variables and interaction terms expanded out
`longdat2`	longitudinal dataset with original variables
`survdat2`	survival dataset with original variables

a list containing four ordered versions of the inputted datasets. In the output long.s is the the ordered version of longdat, surv.s is the ordered version of survdat, long.s2 is the ordered version of longdat2, and surv.s2 is the ordered version of survdat2.