[R] grep

[Steven Yen]

Thank to Rui, Jeff, and Bert. They are all very useful.
Somewhat related is the following, in which jindex is a numeric or 
alphanumeric vector in a function that starts with

try<-function(...., jindex=NA)

In the if loop, in the first line I am trying to determine whether the 
vector jindex is NA;
In the second line, I am trying to determine whether elements in vector 
jindex is are all non-numeric.

Not sure how so I tried to judge by the first element of jindex. Any 
better way? Thannks.

   if (!is.na(jindex[1])){       # like to improve this line
     if(!is.numeric(jindex)[1]){ # like to improve this line
       words  <-jindex
       pattern<-paste(words,collapse="|")
       jindex <-grep(pattern=pattern,x.label,value=FALSE)
     }
     jj<-jindex; x.label<-x.label[jj]
   }

On 2021/5/9 上午 03:02, Rui Barradas wrote:
> Hello,
>
> The pattern can be assembled with paste(., collapse = "|").
> With the same vector of names, nms:
>
>
> words <- c("black","conserv")
> pattern <- paste(words, collapse = "|")
> grep(pattern = pattern, nms, value = TRUE)
> #[1] "x1.black"   "x1.conserv" "x2.black"   "x2.conserv"
>
>
> Hope this helps,
>
> Rui Barradas
>
> Às 18:20 de 08/05/21, Jeff Newmiller escreveu:
>> Regular expression patterns are not vectorized... only the data to be 
>> searched are. Use one of the many websites dedicated to tutoring 
>> regular expressions to learn how they work. (Using function names 
>> like "names" as data names is bad practice.)
>>
>> nms <- c( "x1.one", "x1.black", "x1.othrrace", "x1.moddkna", 
>> "x1.conserv", "x1.nstrprty", "x1.strrep", "x1.sevngprt", "x2.one", 
>> "x2.black", "x2.othrrace", "x2.moddkna", "x2.conserv", "x2.nstrprty", 
>> "x2.strrep", "x2.sevngprt" )
>>
>> grep( "black|conserv", nms, value = TRUE )
>>
>> On May 8, 2021 10:00:12 AM PDT, Steven Yen <styen using ntu.edu.tw> wrote:
>>> Below, the first command simply creates a list of 16 names (labels)
>>> which can be ignore.
>>>
>>> In the 2nd and 3rd commands, I am able to identify names containing
>>> "black".
>>>
>>> In line 4, I am trying to identify names containing "black" or
>>> "conserv"
>>> but obviously it does not work. Can someone help? Thanks.
>>>
>>>> names<-names(tp.nohs$estimate)[c(1:8,58:65)]; names
>>>   [1] "x1.one"      "x1.black"    "x1.othrrace" "x1.moddkna"
>>> "x1.conserv"  "x1.nstrprty"
>>>   [7] "x1.strrep"   "x1.sevngprt" "x2.one"      "x2.black" 
>>> "x2.othrrace"
>>>
>>> "x2.moddkna"
>>> [13] "x2.conserv"  "x2.nstrprty" "x2.strrep"   "x2.sevngprt"
>>>> grep("black",names,value=TRUE)
>>> [1] "x1.black" "x2.black"
>>>> grep("black",names,value=FALSE)
>>> [1]  2 10
>>>> grep(c("black","conserv"),names,value=TRUE)
>>> [1] "x1.black" "x2.black"
>>> Warning message:
>>> In grep(c("black", "conserv"), names, value = TRUE) :
>>>    argument 'pattern' has length > 1 and only the first element will be
>>> used
>>>
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>>