[R] Symbol/String comparison in R
Rui Barradas
ru|pb@rr@d@@ @end|ng |rom @@po@pt
Thu Apr 14 21:01:31 CEST 2022
Hello,
1) The best I could find on lower case/upper case is [1];
The Wikipedia page you link to is about a code page and the collating
sequence is the same as ASCII so no, that's not it.
2) In the cp1252 table "A" < "a", it follows the numeric order 0x31 <
0x41. But what R is using is the locale LC_COLLATE setting, not the "C"
one.
How to validate the end results? The best way is to check the current
setting, with Sys.getlocale.
[1]
https://books.google.pt/books?id=GkajBQAAQBAJ&pg=PA259&lpg=PA259&dq=collating+sequence+portuguese&source=bl&ots=fVnUYHz0ev&sig=ACfU3U3xjpJfPNcWEfvwb_2nScYb89CeOw&hl=pt-PT&sa=X&ved=2ahUKEwiAoNTW-JP3AhVI1xoKHXT-C4oQ6AF6BAgUEAM#v=onepage&q=collating%20sequence%20portuguese&f=false
Hope this helps,
Rui Barradas
Às 16:33 de 14/04/2022, Kristjan Kure escreveu:
> Hi Rui
>
> Thank you for the code snippet.
>
> 1) How do you find your "Portuguese_Portugal.1252" symbols table now?
> Is it this https://en.wikipedia.org/wiki/Windows-1252
> <https://en.wikipedia.org/wiki/Windows-1252>?
>
> 2) What attributes and values do you check to validate the end result?
> I see there is a section "Codepage layout" and I can find "A" and "a"
> symbols.
>
> What values on that table tell you "A" is bigger than "a"?
> "A" < "a" # returns FALSE
> "A" > "a" # returns TRUE
>
> PS! My locale is Estonian_Estonia.1257
>
> Regards,
> Kristjan
>
> On Thu, Apr 14, 2022 at 5:05 PM Rui Barradas <ruipbarradas using sapo.pt
> <mailto:ruipbarradas using sapo.pt>> wrote:
>
> Hello,
>
> This is a locale issue, you are counting on the ASCII table codes but
> that's only valid for the "C" locale.
>
> old_loc <- Sys.getlocale("LC_COLLATE")
>
> "A" < "a"
> #> [1] FALSE
> "A" > "a"
> #> [1] TRUE
>
> Sys.setlocale("LC_COLLATE", locale = "C")
> #> [1] "C"
>
> "A" < "a"
> #> [1] TRUE
> "A" > "a"
> #> [1] FALSE
>
> Sys.setlocale("LC_COLLATE", old_loc)
> #> [1] "Portuguese_Portugal.1252"
>
>
> Hope this helps,
>
> Rui Barradas
>
> Às 15:06 de 13/04/2022, Kristjan Kure escreveu:
> > Hi!
> >
> > Sorry, I am a beginner in R.
> >
> > I was not able to find answers to my questions (tried Google, Stack
> > Overflow, etc). Please correct me if anything is wrong here.
> >
> > When comparing symbols/strings in R - raw numeric values are compared
> > symbol by symbol starting from left? If raw numeric values are
> not used is
> > there an ASCII / Unicode table where symbols have
> values/ranking/order and
> > R compares those values?
> >
> > *2) Comparing symbols*
> > Letter "a" raw value is 61, letter "b" raw value is 62? Is this
> correct?
> >
> > # Raw value for "a" = 61
> > a_raw <- charToRaw("a")
> > a_raw
> >
> > # Raw value for "b" = 62
> > b_raw <- charToRaw("b")
> > b_raw
> >
> > # equals TRUE
> > "a" < "b"
> >
> > Ok, so 61 is less than 62 so it's TRUE. Is this correct?
> >
> > *3) Comparing strings #1*
> > "1040" <= "12000"
> >
> > raw_1040 <- charToRaw("1040")
> > raw_1040
> > #31 *30* (comparison happens with the second symbol) 34 30
> >
> > raw_12000 <- charToRaw("12000")
> > raw_12000
> > #31 *32* (comparison happens with the second symbol) 30 30 30
> >
> > The symbol in the second position is 30 and it's less than 32.
> Equals to
> > true. Is this correct?
> >
> > *4) Comparing strings #2*
> > "1040" <= "10000"
> >
> > raw_1040 <- charToRaw("1040")
> > raw_1040
> > #31 30 *34* (comparison happens with third symbol) 30
> >
> > raw_10000 <- charToRaw("10000")
> > raw_10000
> > #31 30 *30* (comparison happens with third symbol) 30 30
> >
> > The symbol in the third position is 34 is greater than 30. Equals
> to false.
> > Is this correct?
> >
> > *5) Problem - Why does this equal FALSE?*
> > *"A" < "a"*
> >
> > 41 < 61 # FALSE?
> >
> > # Raw value for "A" = 41
> > A_raw <- charToRaw("A")
> > A_raw
> >
> > # Raw value for "a" = 61
> > a_raw <- charToRaw("a")
> > a_raw
> >
> > Why is capitalized "A" not less than lowercase "a"? Based on raw
> values it
> > should be. What am I missing here?
> >
> > Thanks
> > Kristjan
> >
> > [[alternative HTML version deleted]]
> >
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