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Splitting a set of vectors in a list

15 messages · Erik Iverson, Henrique Dallazuanna, Benilton Carvalho +3 more

John Kane
# 
I have a set of character vectors of uneven length
that I have stored in a list.  I can easily enough get
any column of them  using lapply but what I want is to
be able to create a matrix of them.  Other than some
kind of brute force looping approach I have drawn a
blank. 

Would somebody please suggest something? Thanks
 
Example.

mylist <- list(aa=c("cat","peach" ), bb=c("dog",
"apple", "iron"), 
         cc = c("rabbit", "orange", "zinc", "silk"))
myfun <- function(dff) dff[1]       
vect1  <- unlist(lapply(mylist, myfun))


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Erik Iverson
# 
What would you want your output matrix to look like given mylist?
John Kane wrote:
Henrique Dallazuanna
# 
If I understand correctly, try this:

as.data.frame(lapply(mylist, `[`, 1:max(unlist(lapply(mylist, length)))))
On 13/03/2008, John Kane <jrkrideau at yahoo.ca> wrote:

  
    

      
      
    

  


  


      

    

    

      
      

        


  

        

      John Kane
    

    

      
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Ideally something like this:
======================================================
t(cbind( c("cat" ,  "peach" , NA, NA), bbb  <- c("dog"
,  "apple" ,"iron", NA),
ccb <- c("rabbit" ,"orange" ,"zinc" ,  "silk" ))) 

======================================================

Thanks

        
--- Erik Iverson <iverson at biostat.wisc.edu> wrote:

        

            

      
      
      
    

        

      
      
    

        

      
      
    

        
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      John Kane
    

    

      
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My thanks to Henrique Dallazuanna and Phil Spector. 
Both solutions worked well. 
Phil suggested that an alterative to my function would
be 
vect1 = sapply(mylist,'[[',1)
and I see that Henrique used `[` in his solution.

Can you point me to some documentation that discusses
these usages. I have seen them before but I have never
actually figured out how to use them.? 

Thanks.

Problem and solutions
========================================================
mylist <- list(aa=c("cat","peach" ), bb=c("dog",
"apple", "iron"), 
         cc = c("rabbit", "orange", "zinc", "silk"))
myfun <- function(dff) dff[1]       
vect1  <- unlist(lapply(mylist, myfun))

# Desired output
t(cbind( c("cat" ,  "peach" , NA, NA), bbb  <- c("dog"
,  "apple" ,"iron", NA),
ccb <- c("rabbit" ,"orange" ,"zinc" ,  "silk" ))) 

# Phil Spector's approach
mlen = max(sapply(mylist,length))
eqlens = lapply(mylist,function(x)if(length(x) < mlen)
                           
c(x,rep('',mlen-length(x))) else x)
do.call(rbind,eqlens)

# 	"Henrique Dallazuanna" <wwwhsd at gmail.com>
#    I added the t()
t(as.data.frame(lapply(mylist, `[`,
1:max(unlist(lapply(mylist,
 length))))))


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      Henrique Dallazuanna
    

    

      
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On 13/03/2008, John Kane <jrkrideau at yahoo.ca> wrote:

            

      
      
      
    

        
See ?Extract

            

      
      
      
    

        

  
    

      
      
    

  


  


      

    

    

      
      

        


  

        

      Benilton Carvalho
    

    

      
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or the suggestive :)

?"["

b

        
On Mar 13, 2008, at 2:58 PM, Henrique Dallazuanna wrote:

        

            

      
      
      
    

  
  


  


      

    

    

      
      

        


  

        

      John Kane
    

    

      
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Ah ?Extract.  Thanks 

Unless I'm missing something there is nothing  in the
Usage or Examples to suggest to a naive reader like me
that one can use an unbalanced [ or [[, that is
withoug a corresponding ] or ]]. 

I probably am just not understanding the details.

        
--- Henrique Dallazuanna <wwwhsd at gmail.com> wrote:

        

            

      
      
      
    

        
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      Henrique Dallazuanna
    

    

      
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A example:

x <- rnorm(5)

x[3]
`[`(x, 3)
`[[`(x, 3)

x[3:4]
`[`(x, 3:4)
`[[`(x, 3:4) # Error

        
On 13/03/2008, John Kane <jrkrideau at yahoo.ca> wrote:

            

      
      
      
    

        

      
      
    

        

  
    

      
      
    

  


  


      

    

    

      
      

        


  

        

      John Kane
    

    

      
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Blood ell !  Thanks very much, it does help give a
feel for what's happening.  I'll have to do some
experimenting.

        
--- Henrique Dallazuanna <wwwhsd at gmail.com> wrote:

        

            

      
      
      
    

        
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      Bert Gunter
    

    

      
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?"["  ?InternalMethods

x[i,j] is just shorthand for  "["(x,i,j) . (AFAIK)**All** operators
(+,-,...,subscripting,...) in R are functions, stemming from its LISP-like
heritage, and can actually called by the usual functional syntax, f(...),
instead of the operator syntax.

Not sure where this is explicitly discussed within R's documentation, but
you can find info on it in V&R's "S Programming", esp. p.24 and 4.3,
"Extracting or replacing coefficients".

No doubt, other S/R  books explain it also.

Cheers,

Bert Gunter
Genentech Nonclinical Statistics
47374


-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On
Behalf Of John Kane
Sent: Thursday, March 13, 2008 11:53 AM
To: Henrique Dallazuanna
Cc: R R-help
Subject: Re: [R] Splitting a set of vectors in a list (Solved )

My thanks to Henrique Dallazuanna and Phil Spector. 
Both solutions worked well. 
Phil suggested that an alterative to my function would
be 
vect1 = sapply(mylist,'[[',1)
and I see that Henrique used `[` in his solution.

Can you point me to some documentation that discusses
these usages. I have seen them before but I have never
actually figured out how to use them.? 

Thanks.

Problem and solutions
========================================================
mylist <- list(aa=c("cat","peach" ), bb=c("dog",
"apple", "iron"), 
         cc = c("rabbit", "orange", "zinc", "silk"))
myfun <- function(dff) dff[1]       
vect1  <- unlist(lapply(mylist, myfun))

# Desired output
t(cbind( c("cat" ,  "peach" , NA, NA), bbb  <- c("dog"
,  "apple" ,"iron", NA),
ccb <- c("rabbit" ,"orange" ,"zinc" ,  "silk" ))) 

# Phil Spector's approach
mlen = max(sapply(mylist,length))
eqlens = lapply(mylist,function(x)if(length(x) < mlen)
                           
c(x,rep('',mlen-length(x))) else x)
do.call(rbind,eqlens)

# 	"Henrique Dallazuanna" <wwwhsd at gmail.com>
#    I added the t()
t(as.data.frame(lapply(mylist, `[`,
1:max(unlist(lapply(mylist,
 length))))))


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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.

  
  


  


      

    

    

      
      

        


  

        

      Liaw, Andy
    

    

      
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From: Bert Gunter

            

      
      
      
    

        
That is true even for assignment:

R> "<-"(junk, 1:3)
R> junk
[1] 1 2 3

and "{":

R> "{"(1, 2, 3)
[1] 3


I believe this is in the (draft) R Language Definition, part of the
official manuals that shipped with R.

Andy

            

      
      
      
    

        

      
      
    

        
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      John Kane
    

    

      
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--- "Liaw, Andy" <andy_liaw at merck.com> wrote:

        

            

      
      
      
    

        
Okay I think I've got this one but

            

      
      
      
    

        
this defeats me. I see what it is doing but I have not
the slightest idea why . 

I had a look at ?"{" and if I am understanding the
example {2+3; 4+5}  what is happening is that anything
within the {} is being executed as separate statments
but I have not the slightest idea of what is happening
when "{"(1, 2, 3) returns 3.  

The other thing is, is it worth trying to figure out
what appears to be rather esotheric coding if I can do
the same with more intuitively understood albeit
clumsier code?

            

      
      
      
    

        
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      Liaw, Andy
    

    

      
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From: John Kane

            

      
      
      
    

        
The value of "{" is simply the last statement inside.  This is basically
the reason why when one writes a function, one can simply type the name
of the object (or the expression) to be returned as the last line,
instead of having to wrap that in return().

            

      
      
      
    

        
I do not believe anyone in his/her right mind would write code that way
(except those with very developed left brain that can code in LISP-like
languages).  To me the point is more about understanding what these
things do, so you can use them in perhaps some creative ways (but not to
the point of abusing it, of course).

Andy

            

      
      
      
    

        

      
      
    

            

      
      
      
    

        

      
      
    

            

      
      
      
    

        
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      John Kane
    

    

      
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--- "Liaw, Andy" <andy_liaw at merck.com> wrote:

        

            

      
      
      
    

        
Very simple when explained. Thanks very much. 

So then, all that } is doing is signifiying the end of
{ ?

            

      
      
      
    

        
Given some of the responses in R-help a naive user
like should perhaps be excused for thinking that some
of the things are writen is a slightly esorteric
manner.

            

      
      
      
    

        
========================================================