Thanks a million, Milan!!! Hongwei
On Tuesday, November 15, 2016 at 1:32:36 PM UTC-5, Milan Bouchet-Valat wrote: > > Le lundi 14 novembre 2016 à 14:18 -0800, Hongwei Liu a écrit : > > Hi guys, > > > > I am new to Julia and I have trouble in finding a similar function in > > Julia that has the ability of "update" in R. > > > > For example, set formula = y ~ x1 + x2 > > > > In R, I can use update(formula, D ~ . ) to change the formula from y > > ~ x1 + x2 to D ~ x1 + x2 > > > > In Julia, the formula's type is DataFrames.Formula and I have > > searched online and Dataframes document for a long time but still > > couldn't find the answer. > > > > So my question is: > > > > Is there are such a function in Julia? If not, is there a way to > > modify a formula directly? > I don't think we provide such a function yet, but you can easily do > that manually. > > Use dump() to see what the formula object consists in: > julia> dump(y ~ x1 + x2) > DataFrames.Formula > lhs: Symbol y > rhs: Expr > head: Symbol call > args: Array{Any}((3,)) > 1: Symbol + > 2: Symbol x1 > 3: Symbol x2 > typ: Any > > Here, you can just change the rhs (right hand side) argument: > julia> f = y ~ x1 + x2 > Formula: y ~ x1 + x2 > > julia> f.lhs = :D > :D > > julia> f > Formula: D ~ x1 + x2 > > > Regards > > > Thanks a lot!! > > > > Hongwei >