[R] Odp: {R} How to extract correctly from vector?

[Petr PIKAL]

> 
> Dear list,
> 
> 
> 
> I have problem that I cannot solve and would like to ask your opinion. I
> tried to ask a few days ago already but got no answer and all my 
attempts to
> solve it by myself since then failed. Sorry for repeated posting! Here 
the
> problem broken down a bit.
> 
> 
> 
> My problem basically is, that I want to use the elements of a character
> vector as names for objects and by recalling only the subscript of the
> character vector get the object information I assigned.
> 
> 
> 
> Example:
> 
> 
> 
> vector of names created as follows:
> 
> char <- paste("A",1,sep="")
> 
> for (i in 2:10) {char[i] <- paste("A",i,sep="")}
> 
> char 
> 
> [1] "A1"  "A2"  "A3"  "A4"  "A5"  "A6"  "A7"  "A8"  "A9"  "A10"

Slightly better

 char <- paste("A",1:10,sep="")


> 
> Now assign each element as name for a data frame:
> 
> (d <-
> 
data.frame(cbind(X1=1,Y1=1:10,X2=1,Y2=1:10,X3=1,Y3=1:10,X4=1,Y4=1:10,X5=1,Y5
> =1:10,
> 
> 
> X6=1,Y6=1:10,X7=1,Y7=1:10,X8=1,Y8=1:10,X9=1,Y9=1:10,X10=1,Y10=1:10)))

One right parentheses more.

> 
> x <- paste("X",1,sep="")
> 
> y <- paste("Y",1,sep="")
> 
> for (i in 2:10) {x[i] <- paste("X",i,sep="")
> 
>                  y[i] <- paste("Y",i,sep="")}

Maybe you wanted

x <- paste("X",1:10,sep="")
y <- paste("Y",1:10,sep="")


> 
> for (k in 1:10) {assign(char[k],d[,c(x[k],y[k])])}

I would use list.

lll<- vector(mode="list", 10)
names(lll) <- char
for(k in 1:10) lll[[k]] <- d[,c(x[k],y[k])]

instead of many An objects you have one object with names An and you can 
easily subset it.

lll[[1]]
lll[["A5"]]

> 
> 
> 
> If I call "A1", I get a dataframe with columns "X1" and "Y1", so far so
> good.
> 
> 
> 
> Now the trouble part:
> 
> nam <- paste("test",1,sep="")
> 
> for (i in 2:10) {nam[i] <- paste("test",i,sep="")}

nam <- paste("test",1:10,sep="")


> 
> 
> 
> for (i in 1:10){assign(nam[i],as.ltraj(xy=char[1],date=DATE,...)

So the same applies here

lll<- vector(mode="list", 10)
names(lll) <- char
for (i in 1:10) lll[[i]] <- as.ltraj(xy=char[i],date=DATE,...)

However I do not know as.ltraj which may require different input of 
parameters.

Anyway in this case are lists by my opinion the only way to be able to 
handle such things smoothly and without much headache.

Regards
Petr


> ????????????
> 
> 
> 
> Please don't get carried away by as.ltraj, it's an object type of the
> package adehabitat to analyze animal tracks. However, I need to feed it 
the
> xy (coordination) information in form of a data frame. I have 20 animals 
to
> analyze (per different setup), so I want it to work in a handier way 
than
> keep pushing buttons. By the way I handle it now, I only hand over the 
term
> "A1" but not the data frame "A1".
> 
> 
> 
> How can I solve this. Turning the vector into a list does not work and I 
am
> not sure if there's something I can do...
> 
> 
> 
> Please help if you can! Many thanks in advance already.
> 
> 
> 
> Jacqueline
> 
> 
> 
> 
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> 
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