Assignments inside lapply

Dear Alex,

I think you want to use apply()

ij <- expand.grid(i = seq_len(dimx),j = seq_len(dimy))
Powermap <- apply(ij, 1, function(x){
	Pr(x, c(PRX, PRY), f)
})

Best regards,

Thierry

----------------------------------------------------------------------------
ir. Thierry Onkelinx
Instituut voor natuur- en bosonderzoek
team Biometrie & Kwaliteitszorg
Gaverstraat 4
9500 Geraardsbergen
Belgium

Research Institute for Nature and Forest
team Biometrics & Quality Assurance
Gaverstraat 4
9500 Geraardsbergen
Belgium

tel. + 32 54/436 185
Thierry.Onkelinx at inbo.be
www.inbo.be

To call in the statistician after the experiment is done may be no more than asking him to perform a post-mortem examination: he may be able to say what the experiment died of.
~ Sir Ronald Aylmer Fisher

The plural of anecdote is not data.
~ Roger Brinner

The combination of some data and an aching desire for an answer does not ensure that a reasonable answer can be extracted from a given body of data.
~ John Tukey

-----Oorspronkelijk bericht-----
Van: r-help-bounces at r-project.org 
[mailto:r-help-bounces at r-project.org] Namens Alaios
Verzonden: woensdag 27 april 2011 11:37
Aan: R-help at r-project.org
Onderwerp: [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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