[R] Symbol/String comparison in R

[Rui Barradas]

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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