[R] Determine the Length of the Longest Word in a String

[Marc Schwartz]

On Apr 10, 2009, at 3:40 PM, Shadley Thomas wrote:

> Hi Everyone,
>
> I'm new to programming R and have accomplished my goal, but feel  
> that there
> is probably a more efficient way of coding this.  I'd appreciate any
> guidance that a more advanced programmer can provide.
>
> My goal --
> I would like to find the length of the longest word in a string  
> containing
> many words separated by spaces.
>
> How I did it --
> I was able to find the length of the longest word by parsing the  
> string into
> a list of separate words, using the function "which.max" to  
> determine the
> element with the longest length, and then using "nchar" to calculate  
> the
> length of that particular word.
>
> My question --
> It seems inefficient to determine which element is the longest and  
> then
> calculate the length of that longest element.  I was hoping to find  
> a way to
> simply return the length of the longest word in a more  
> straightforward way.
>
> Short sample code --
>> shadstr <- c("My string of words with varying lengths.  Longest  
>> word is
> nine - 1 22 333 999999999 4444")
>> shadvector <- unlist(strsplit(shadstr, split=" "))
>> shadvlength <- lapply(shadvector,nchar)
>> shadmaxind <- which.max(shadvlength) ## Maximum element
>> shadmax <- nchar(shadvector[shadmaxind])
>> shadmax
> [1] 9
>
> Many thanks for your help and suggestions.
> Shad

Welcome to R Shad.

Note that the 'x' argument to nchar() can be a vector, which means  
that it will return the character lengths of the individual elements  
of the vector. Thus:

# Get the individual components, I use list indexing here, but  
unlist() works as well
 > strsplit(shadstr, " ")[[1]]
  [1] "My"        "string"    "of"        "words"     "with"
  [6] "varying"   "lengths."  ""          "Longest"   "word"
[11] "is"        "nine"      "-"         "1"         "22"
[16] "333"       "999999999" "4444"

# Get the lengths of each
 > nchar(strsplit(shadstr, " ")[[1]])
  [1] 2 6 2 5 4 7 8 0 7 4 2 4 1 1 2 3 9 4

# Get the max length
 > max(nchar(strsplit(shadstr, " ")[[1]]))
[1] 9


As an aside, note that there are two spaces between the period '.' and  
the word "Longest", which results in an empty element in the resultant  
vector. If you wanted to split on one or more spaces, you could use a  
'regular expression' in strsplit() such as:

 > strsplit(shadstr, " +")[[1]]
  [1] "My"        "string"    "of"        "words"     "with"
  [6] "varying"   "lengths."  "Longest"   "word"      "is"
[11] "nine"      "-"         "1"         "22"        "333"
[16] "999999999" "4444"

In the above, the use of " +" says to match one or more spaces as the  
split character. See ?regex for more information on that point.

HTH,

Marc Schwartz