R help - Feb 2009 - Loop on characters

Hi,

suppose I have three vectors like :

l1 = 1:4
l2 = 4:9
l3 = 16:67

now I want to construct a loop like :

for (i in 1:3)
   {
     count1[i] = length(li) # i.e. it will take l1, l2, l3 according to
value of i
   }

Can anyone please tell me how to do that?

Regards,

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megh wrote:
> 
> suppose I have three vectors like :
> 
> l1 = 1:4
> l2 = 4:9
> l3 = 16:67
> 
> now I want to construct a loop like :
> 
> for (i in 1:3)
>    {
>      count1[i] = length(li) # i.e. it will take l1, l2, l3 according to
> value of i
>    }
> 
Try this. There's probably a more elegant way to do it, but this works.

l1 <- 1:4; l2 <- 4:9;  l3 <- 16:67
count1 <- c( ) # start with an empty vector
for (i in 1:3) count1[i] <-
length(get(paste("l",i,sep="")))
count1

The call to paste( ) concatenates the letter "l" and value of i; they
are
separated by the null string (otherwise they would have the default blank
separator between them).  The call to get( ) fetches the object with that
name.


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megh -
    The best way to organize similar objects in R is to
put them into a list.  If you keep this in mind when you're
first organizing your data, it's no harder than giving each object
a separate name.  For example
> l = list(l1,l2,l3)
The reason that this is a good idea in R is that functions
like sapply, lapply, and mapply automatically operate on each
element of a list, and return the answer in a suitable R object. 
(Note that in your example, you would get an error because you 
hadn't defined count1.  And why should you?)

So the answer you want is
> count1 = sapply(l,length)
> count1
[1]  4  6 52

Hope this helps.
                                        - Phil Spector
 					 Statistical Computing Facility
 					 Department of Statistics
 					 UC Berkeley
 					 spector at stat.berkeley.edu





On Tue, 10 Feb 2009, megh wrote:
>
> Hi,
>
> suppose I have three vectors like :
>
> l1 = 1:4
> l2 = 4:9
> l3 = 16:67
>
> now I want to construct a loop like :
>
> for (i in 1:3)
>   {
>     count1[i] = length(li) # i.e. it will take l1, l2, l3 according to
> value of i
>   }
>
> Can anyone please tell me how to do that?
>
> Regards,
>
> --
> View this message in context:
http://www.nabble.com/Loop-on-characters-tp21949173p21949173.html
> Sent from the R help mailing list archive at Nabble.com.
>
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