R help - Apr 2015 - regexpr - ignore all special characters and punctuation in a string

Hello!

Please point me in the right direction.
I need to match 2 strings, but focusing ONLY on characters, ignoring
all special characters and punctuation signs, including (), "", etc..

For example:
I want the following to return: TRUE

"What a nice day today! - Story of happiness: Part 2." =   "What
a nice day today: Story of happiness (Part 2)"


-- 
Thank you!
Dimitri Liakhovitski

I think I found a partial answer:

str_replace_all(x, "[[:punct:]]", " ")

On Mon, Apr 20, 2015 at 9:59 AM, Dimitri Liakhovitski
<dimitri.liakhovitski at gmail.com> wrote:
> Hello!
>
> Please point me in the right direction.
> I need to match 2 strings, but focusing ONLY on characters, ignoring
> all special characters and punctuation signs, including (), "",
etc..
>
> For example:
> I want the following to return: TRUE
>
> "What a nice day today! - Story of happiness: Part 2." =>   
"What a nice day today: Story of happiness (Part 2)"
>
>
> --
> Thank you!
> Dimitri Liakhovitski


-- 
Dimitri Liakhovitski

> On Apr 20, 2015, at 8:59 AM, Dimitri Liakhovitski <dimitri.liakhovitski
at gmail.com> wrote:
> 
> Hello!
> 
> Please point me in the right direction.
> I need to match 2 strings, but focusing ONLY on characters, ignoring
> all special characters and punctuation signs, including (), "",
etc..
> 
> For example:
> I want the following to return: TRUE
> 
> "What a nice day today! - Story of happiness: Part 2." =>  
"What a nice day today: Story of happiness (Part 2)"
> 
> 
> -- 
> Thank you!
> Dimitri Liakhovitski

Look at ?agrep:

Vec1 <- "What a nice day today! - Story of happiness: Part 2."
Vec2 <- "What a nice day today: Story of happiness (Part 2)?

# Match the words, not the punctuation.
# Not fully tested
> agrep("What a nice day today Story of happiness Part 2", c(Vec1,
Vec2))
[1] 1 2
> agrep("What a nice day today Story of happiness Part 2", c(Vec1,
Vec2),
        value = TRUE)
[1] "What a nice day today! - Story of happiness: Part 2."
[2] "What a nice day today: Story of happiness (Part 2)?  


Also, possibly:

  http://cran.r-project.org/web/packages/stringdist


Regards,

Marc Schwartz

Hi Dimitri,

str_replace_all is not in the base libraries, you could use 'gsub' as
well,
for example:

a = "What a nice day today! - Story of happiness: Part 2."
b = "What a nice day today: Story of happiness (Part 2)"
sa = gsub("[^A-Za-z0-9]", "", a)
sb = gsub("[^A-Za-z0-9]", "", b)
a==b
# [1] FALSE
sa==sb
# [1] TRUE

Take care of the extra space in a after the '-', so also replace
spaces...

Best,
Sven.

On 20 April 2015 at 16:05, Dimitri Liakhovitski <
dimitri.liakhovitski at gmail.com> wrote:
> I think I found a partial answer:
>
> str_replace_all(x, "[[:punct:]]", " ")
>
> On Mon, Apr 20, 2015 at 9:59 AM, Dimitri Liakhovitski
> <dimitri.liakhovitski at gmail.com> wrote:
> > Hello!
> >
> > Please point me in the right direction.
> > I need to match 2 strings, but focusing ONLY on characters, ignoring
> > all special characters and punctuation signs, including (),
"", etc..
> >
> > For example:
> > I want the following to return: TRUE
> >
> > "What a nice day today! - Story of happiness: Part 2." =>
>    "What a nice day today: Story of happiness (Part 2)"
> >
> >
> > --
> > Thank you!
> > Dimitri Liakhovitski
>
>
>
> --
> Dimitri Liakhovitski
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
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On 20/04/2015 9:59 AM, Dimitri Liakhovitski wrote:
> Hello!
> 
> Please point me in the right direction.
> I need to match 2 strings, but focusing ONLY on characters, ignoring
> all special characters and punctuation signs, including (), "",
etc..
> 
> For example:
> I want the following to return: TRUE
> 
> "What a nice day today! - Story of happiness: Part 2." =>   
"What a nice day today: Story of happiness (Part 2)"
> 
> 
I would transform both strings using gsub(), then compare.

e.g.

clean <- function(s)
  gsub("[[:punct:][:blank:]]", "", s)

clean("What a nice day today! - Story of happiness: Part 2.")
=clean("What a nice day today: Story of happiness (Part 2)")

This completely ignores spaces; you might want something more
sophisticated if you consider "today" and "to day" to be
different, e.g.

clean <- function(s) {
  s <- gsub("[[:punct:]]", "", s)
  gsub("[[:blank:]]+", " ", s)
}

which converts multiple blanks into single spaces.

Duncan Murdoch

On Mon, Apr 20, 2015 at 8:59 AM, Dimitri Liakhovitski <
dimitri.liakhovitski at gmail.com> wrote:
> Hello!
>
> Please point me in the right direction.
> I need to match 2 strings, but focusing ONLY on characters, ignoring
> all special characters and punctuation signs, including (), "",
etc..
>
> For example:
> I want the following to return: TRUE
>
> "What a nice day today! - Story of happiness: Part 2." =>   
"What a nice day today: Story of happiness (Part 2)"
>
>
> --
> Thank you!
> Dimitri Liakhovitski
>
>
>
?Perhaps a variation on:
> str1<-"What a nice day today! - Story of happiness: Part 2."
> str2<- "What a nice day today: Story of happiness (Part 2)"
>
gsub('[^[:alpha:]]','',str1)==gsub('[^[:alpha:]]','',str2)
[1] TRUE
>
The gsub() removes all characters which are not alphabetic from each string
and then compares them.?


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