Re: [R] Assignments inside lapply

From: Nick Sabbe <nick.sabbe_at_ugent.be>
Date: Wed, 27 Apr 2011 11:58:56 +0200

No, that does not work.
You cannot do assignment within (l)apply.
Nor in any other function for that matter.

Nick Sabbe

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-----Original Message-----
From: r-help-bounces_at_r-project.org [mailto:r-help-bounces_at_r-project.org] On
Behalf Of Alaios
Sent: woensdag 27 april 2011 11:37
To: R-help_at_r-project.org
Subject: [R] Assignments inside lapply

Dear all I would like to ask you if an assignment can be done inside a
lapply statement.

For example

I would like to covert a double nested for loop

for (i in c(1:dimx)){ 
  for (j in c(1:dimy)){
      Powermap[i,j] <- Pr(c(i,j),c(PRX,PRY),f)
   }
}

to something like that:


ij<-expand.grid(i=seq(1:dimx),j=(1:dimy))

unlist(lapply(1:nrow(ij),function(rowId) { return
(Powermap[i,j]<-Pr(c(ij$i[rowId],ij$j[rowId]),c(PRX,PRY),f))   }))


as you can see lapply does not return nothing as the assignment is done
inside the function. Would that work correctly? What are the cases such a
statement will misfunction?

I would like to thank you in advace for your help.

Best Regards
Alex


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Received on Wed 27 Apr 2011 - 10:06:59 GMT

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