Help to make a for for index

Hi,

I try to make a vector in a for for loop, but it dont work.

Look:
a <- 0;for(i in c(1:2)) { for(j in c(1:2)) { a <- i+j; print(a)}}
[1] 2
[1] 3
[1] 3
[1] 4

I try to make this a vector, like this:
[1] 2 3 3 4
a <- 0;for(i in c(1:2)) { for(j in c(1:2)) { a[j] <- i+j}}; print(a)
[1] 3 4
a <- 0;for(i in c(1:2)) { for(j in c(1:2)) { a[i] <- i+j}}; print(a)
[1] 3 4

In this way the vector have only the two last loop.

I try another way but it dont work.

How make a correct index for this loop inside loop?

Thanks
Ronaldo
As coisas por aqui n?o andam, arrastam-se lentamente em dire??o
a lugar nenhum.

Eu hoje acordei assim, otimista...
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"Ronaldo Reis Jr." <chrysopa at insecta.ufv.br> writes:
Hi,

I try to make a vector in a for for loop, but it dont work.

Look:

a <- 0;for(i in c(1:2)) { for(j in c(1:2)) { a <- i+j; print(a)}}
[1] 2
[1] 3
[1] 3
[1] 4

I try to make this a vector, like this:
[1] 2 3 3 4

a <- 0;for(i in c(1:2)) { for(j in c(1:2)) { a[j] <- i+j}}; print(a)
[1] 3 4
a <- 0;for(i in c(1:2)) { for(j in c(1:2)) { a[i] <- i+j}}; print(a)
[1] 3 4

In this way the vector have only the two last loop.

I try another way but it dont work.

How make a correct index for this loop inside loop?
Use a 3rd index:

k <- 0
a <- numeric(4)
for(i in 1:2)
   for(j in 1:2){
       k <- k + 1
       a[k] <- i+j
   }
a

or simply

as.vector(outer(1:2,1:2,"+"))
O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)             FAX: (+45) 35327907
Printing some intermediate expressions can make it clearer what R is trying 
to do:

 > a <- 0;for(i in c(1:2)) { for(j in c(1:2)) { e<-substitute(a[j] <- 
i+j,list(i=i,j=j)); cat("executing:", deparse(e),"\n"); eval(e)}}; print(a)
executing: a[1] <- 1 + 1
executing: a[2] <- 1 + 2
executing: a[1] <- 2 + 1
executing: a[2] <- 2 + 2
[1] 3 4
 >

Perhaps this is what you want: (?)

 > a <- numeric(0);for(i in c(1:2)) { for(j in c(1:2)) { a <- c(a,i+j); 
print(a)}}
[1] 2
[1] 2 3
[1] 2 3 3
[1] 2 3 3 4
 > a
[1] 2 3 3 4
 >

(This is not the most efficient way to construct a vector in a loop, but it 
works and the code captures the spirit of what I'm guessing you were trying 
to do.)

hope this helps,

-- Tony Plate
Hi,

I try to make a vector in a for for loop, but it dont work.

Look:

a <- 0;for(i in c(1:2)) { for(j in c(1:2)) { a <- i+j; print(a)}}
[1] 2
[1] 3
[1] 3
[1] 4

I try to make this a vector, like this:
[1] 2 3 3 4

a <- 0;for(i in c(1:2)) { for(j in c(1:2)) { a[j] <- i+j}}; print(a)
[1] 3 4
a <- 0;for(i in c(1:2)) { for(j in c(1:2)) { a[i] <- i+j}}; print(a)
[1] 3 4

In this way the vector have only the two last loop.

I try another way but it dont work.

How make a correct index for this loop inside loop?

Thanks
Ronaldo
--
As coisas por aqui n?o andam, arrastam-se lentamente em dire??o
a lugar nenhum.

Eu hoje acordei assim, otimista...
--
|   // | \\   [*****************************][*******************]
|| ( ?   ? )  [Ronaldo Reis J?nior          ][PentiumIII-600     ]
|      V      [UFV/DBA-Entomologia          ][HD: 30 + 10 Gb     ]
||  /     \   [36571-000 Vi?osa - MG        ][RAM: 128 Mb        ]
|  /(.''`.)\  [Fone: 31-3899-2532           ][Video: SiS620-8Mb  ]
||/(: :'  :)\ [chrysopa at insecta.ufv.br      ][Modem: Pctel-onboar]
|/ (`. `'` ) \[ICQ#: 5692561                ][Kernel: 2.4.18     ]
||  ( `-  )   [*****************************][*******************]
||| _/   \_Powered by GNU/Debian W/Sarge D+ || Lxuser#: 205366

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Two alternative solutions:

as.vector(outer(1:2, 1:2, "+"))

a <- rep(NA, 4)
i1 <- 0
for(i in 1:2)for(j in 1:2){
	i1 <- i1+1
	a[i1] <- i+j
}
a

hth.  spencer graves
Hi,

I try to make a vector in a for for loop, but it dont work.

Look:

a <- 0;for(i in c(1:2)) { for(j in c(1:2)) { a <- i+j; print(a)}}
[1] 2
[1] 3
[1] 3
[1] 4

I try to make this a vector, like this:
[1] 2 3 3 4

a <- 0;for(i in c(1:2)) { for(j in c(1:2)) { a[j] <- i+j}}; print(a)
[1] 3 4

a <- 0;for(i in c(1:2)) { for(j in c(1:2)) { a[i] <- i+j}}; print(a)
[1] 3 4

In this way the vector have only the two last loop.

I try another way but it dont work.

How make a correct index for this loop inside loop?

Thanks
Ronaldo