Novice needs to loop lm in R

Question

I\'m a PhD student of genetics and I am trying do association analysis of some genetic data using linear regression. In the table below I\'m regressing each \'trait\' agains

Answer 1

Personally I don't find the problem so easy. Specially for an R novice.

Here a solution based on creating dynamically the regression formula. The idea is to use paste function to create different formula terms, y~ x + var + x * var then coercing the result string tp a formula using as.formula. Here y and x are the formula dynamic terms: y in c(trait1,trai2,..) and x in c(SNP1,SNP2,...). Of course here I use lapply to loop.

lapply(1:3,function(i){
 y <- paste0('trait',i)
 x <- paste0('SNP',i)
 factor1 <- x
 factor2 <- 'var'
 factor3 <- paste(x,'var',sep='*')
 listfactor <- c(factor1,factor2,factor3)
 form <- as.formula(paste(y, "~",paste(listfactor,collapse="+")))
 lm(formula = form, data = dat)
})

I hope someone come with easier solution, ore more R-ish one:)

EDIT

Thanks to @DWin comment , we can simplify the formula to just y~x*var since it means y is modeled by x,var and x*var

So the code above will be simplified to :

 lapply(1:3,function(i){
     y <- paste0('trait',i)
     x <- paste0('SNP',i)
     LHS <- paste(x,'var',sep='*')
     form <- as.formula(paste(y, "~",LHS)
     lm(formula = form, data = dat)
    })