[R] Looping an lapply linear regression function

[arun]

HI,
May be this helps:
 set.seed(28)
 dat1<- setNames(as.data.frame(matrix(sample(1:40,10*5,replace=TRUE),ncol=5)),letters[1:5])
indx<-as.data.frame(combn(names(dat1),2),stringsAsFactors=FALSE)
res<-t(sapply(indx,function(x) {x1<-cbind(dat1[x[1]],dat1[x[2]]);summary(lm(x1[,1]~x1[,2]))$coef[,4]}))
 rownames(res)<-apply(indx,2,paste,collapse="_")
 colnames(res)[2]<- "Coef1"
 head(res,3)
#    (Intercept)     Coef1
#a_b  0.39862676 0.8365606
#a_c  0.02427885 0.6094141
#a_d  0.37521423 0.7578723


#permutation
indx2<-expand.grid(names(dat1),names(dat1),stringsAsFactors=FALSE)
#or
indx2<- expand.grid(rep(list(names(dat1)),2),stringsAsFactors=FALSE)
indx2New<- indx2[indx2[,1]!=indx2[,2],]
res2<-t(sapply(seq_len(nrow(indx2New)),function(i) {x1<- indx2New[i,]; x2<-cbind(dat1[x1[,1]],dat1[x1[,2]]);summary(lm(x2[,1]~x2[,2]))$coef[,4]}))
row.names(res2)<-apply(indx2New,1,paste,collapse="_")
 colnames(res2)<- colnames(res)


A.K.


Hi everyone, 

First off just like to say thanks to everyone´s contributions. 
Up until now, I´ve never had to post as I´ve always found the answers 
from trawling through the database. I´ve finally managed to stump 
myself, and although for someone out there, I´m sure the answer to my 
problem is fairly simple, I, however have spent the whole day infront of
 my computer struggling. I know I´ll probably get an absolute ribbing 
for making a basic mistake, or not understanding something fully, but 
I´m blind to the mistake now after looking so long at it. 

What I´m looking to do, is formulate a matrix ([28,28]) of 
p-values produced from running linear regressions of 28 variables 
against themselves (eg a~b, a~c, a~d.....b~a, b~c etc...), if that makes
 sense. I´ve managed to get this to work if I just input each variable 
by hand, but this isn´t going to help when I have to make 20 matrices. 

My script is as follows; 


for (j in [1:28]) 
{ 
 ##This section works perfectly, if I don´t try to loop it, I know 
this wont work at the moment, because I haven´t designated what j is, 
but I´m showing to highlight what I´m attempting to do.   
  

   models <- lapply(varlist, function(x) { 
    lm(substitute(ANS ~ i, list(i = as.name(x))), data = con.i) 
  }) 
  
          abc<- lapply(models, function(f) summary(f)$coefficients[,4]) 
  
          abc<- do.call(rbind, abc) 
  
          
  
} 

I get the following error when I try to loop it... 

Error in model.frame.default(formula = substitute(j ~ i, list(i = as.name(x))),  : 
  variable lengths differ (found for 'ANS') ##ÄNS being my first variable 

All variables are of the same length, with 21 recordings for each 


If anyone can suggest a method of looping, or another means 
or producing ´models´ for each of my 28 variables, without having to do 
it by hand that would be fantastic. 

Thanks in advance!!