Replace subscript number in string

Question

I have the following vector and I want to have the subscript numbers (e.g. ₆, ₂) to be replaced with 'normal' numbers.

vec = c("C₆H₄ClNO₂", "C₆H₆N₂O₂", "C₆H₅NO₃", "C₉H₁₀O₂", "C₈H₈O₃")

I could lookup all subscript values and replace them individually:

gsub('₆', '6', vec)

But isn't there a pattern in regex for it?

There's a similar question for javascript but I couldn't translate it into R.

chartr("₀₁₂₃₄₅₆₇₈₉", "0123456789", vec) — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Sep 19, 2019 at 8:54
@WiktorStribiżew it's not really a duplicate imho, since I'm asking for a pattern in regex for sub/superscripts. But yes, this would be one possibility. — andschar
– andschar, Commented Sep 19, 2019 at 8:57
You need no regex here. chartr is from base R, use it here. — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Sep 19, 2019 at 8:59
Possible duplicate of Using multiple gsubs in one r function — akrun
– akrun, Commented Sep 19, 2019 at 17:51
This question is in my opinion significantly different from the proposed duplicate, which is why I voted to undelete and reopen. Besides, chartr is way too underappreciated and deserves more of our love. — Roman Luštrik
– Roman Luštrik, Commented Sep 25, 2019 at 7:04

Wiktor Stribiżew · Accepted Answer · 2019-09-19 09:04:18Z

6

Use chartr:

Translate characters in character vectors

Solution:

chartr("₀₁₂₃₄₅₆₇₈₉", "0123456789", vec)

See the online R demo

BONUS

To normalize superscript digits use

chartr("⁰¹²³⁴⁵⁶⁷⁸⁹", "0123456789", "⁰¹²³⁴⁵⁶⁷⁸⁹")
## => [1] "0123456789"

answered Sep 19, 2019 at 9:04

Wiktor Stribiżew

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Comments

Ronak Shah · Accepted Answer · 2019-09-19 09:17:56Z

3

We can use str_replace_all from stringr to extract all the subscript numbers, convert it to equivalent integer subtract 8272 (because that is the difference between integer value of ₆ and 6 and all other equivalents) and convert it back.

stringr::str_replace_all(vec, "\\p{No}", function(m) intToUtf8(utf8ToInt(m) - 8272))
#[1] "C6H4ClNO2" "C6H6N2O2"  "C6H5NO3"   "C9H10O2"   "C8H8O3"

As pointed out by @Wiktor Stribiżew "\\p{No}" matches more than subscript digits to only match subscripts from 0-9 we can use (thanks to @thothal )

str_replace_all(vec, "[\U2080-\U2089]", function(m) intToUtf8(utf8ToInt(m) - 8272))

edited Sep 19, 2019 at 9:17

answered Sep 19, 2019 at 9:03

Ronak Shah

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2 Comments

Wiktor Stribiżew Over a year ago

\p{No} matches more than subscript digits and it is not the solution OP needs.

thothal Over a year ago

You should replace your regex to [\U2080-\U2089]

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