sprintf padding with non English symbols - r

Question

I encountered a strange sprintf() behaviour with the non English symbols. I tried padding a strings but I got an unexpected results:
lapply(c("ZZZ", "ZZZZZZ", "ЯЯЯ", "ЯЯЯЯЯЯ"),
function(x) sprintf("%-20s: %s", x, "VALUE"))
#> [[1]]
#> [1] "ZZZ : VALUE"
#>
#> [[2]]
#> [1] "ZZZZZZ : VALUE"
#>
#> [[3]]
#> [1] "ЯЯЯ : VALUE"
#>
#> [[4]]
#> [1] "ЯЯЯЯЯЯ : VALUE"
#>
Anybody can explain why this is happening and how to fix it?
Session info may be useful:
R version 3.2.2 (2015-08-14)
Platform: x86_64-pc-linux-gnu (64-bit)
Running under: Arch Linux
locale:
[1] LC_CTYPE=ru_RU.UTF-8 LC_NUMERIC=C LC_TIME=ru_RU.UTF-8 LC_COLLATE=C
[5] LC_MONETARY=ru_RU.UTF-8 LC_MESSAGES=ru_RU.UTF-8 LC_PAPER=ru_RU.UTF-8 LC_NAME=C
[9] LC_ADDRESS=C LC_TELEPHONE=C LC_MEASUREMENT=ru_RU.UTF-8 LC_IDENTIFICATION=C
attached base packages:
[1] stats graphics grDevices utils datasets methods base
loaded via a namespace (and not attached):
[1] shiny_0.12.2 R6_2.1.1 rsconnect_0.4.1.4 htmltools_0.2.6 tools_3.2.2 Rcpp_0.12.2 digest_0.6.8
[8] xtable_1.8-0 httpuv_1.3.3 mime_0.4

Answer 1

I can tell you why it's happening, but not how to fix it. From the docs for sprintf:
Field widths and precisions of %s conversions are interpreted as bytes, not characters, as described in the C standard.
In UTF-8 the character Я is two bytes (0xD0 0xAF), so "ЯЯЯ" is 6 bytes whereas "ZZZ" is 3 bytes, and sprintf renders them accordingly.
Edit
One workaround is to use sprintf's asterisk feature, which lets you declare the width of a field (in bytes), along with the nchar function, which lets you calculate both the display width and the number of bytes in a string.
So, for example, nchar("ЯЯЯ", "width") and nchar("ЯЯЯ", "bytes") return 3 and 6, respectively. If we want to pad its width to 20 display characters, then we have to give sprintf a width of 23 bytes: 20 plus the number of bytes minus the display width.
sprintf("%-*s", 23, "ЯЯЯ")
#> [1] "ЯЯЯ "
Or:
str <- "ЯЯЯ"
pad.len <- 20 + nchar(str, "bytes") + nchar(str, "width")
sprintf("%-*s", pad.len, str)
#> [1] "ЯЯЯ "
This works for "ZZZ", too, because the bytes and display width are equal, so it comes out to 20:
pad <- function(str) {
pad.len <- 20 + nchar(str, "bytes") - nchar(str, "width")
return(sprintf("%-*s: %s", pad.len, str, "VALUE"))
}
print(lapply(c("ZZZ", "ZZZZZZ", "ЯЯЯ", "ЯЯЯЯЯЯ"), pad))
#> [[1]]
#> [1] "ZZZ : VALUE"
#>
#> [[2]]
#> [1] "ZZZZZZ : VALUE"
#>
#> [[3]]
#> [1] "ЯЯЯ : VALUE"
#>
#> [[4]]
#> [1] "ЯЯЯЯЯЯ : VALUE"
P.S. This is the first R code I've ever written so if you see any ways to improve it please feel free to comment.

Answer 2

I found solution with stri_pad_right() function from stringi package:
lapply(c("ZZZ", "ZZZZZZ", "ЯЯЯ", "ЯЯЯЯЯЯ"),
function(x) paste0(stringi::stri_pad_right(x, 20), ": VALUE"))
#> [[1]]
#> [1] "ZZZ : VALUE"
#>
#> [[2]]
#> [1] "ZZZZZZ : VALUE"
#>
#> [[3]]
#> [1] "ЯЯЯ : VALUE"
#>
#> [[4]]
#> [1] "ЯЯЯЯЯЯ : VALUE"
#>
Update
Another solution based on the #Jordan answer uses only base R functions:
str_pad <- function(str, width = floor(0.9 * getOption("width")),
side = c("left", "both", "right")) {
side <- match.arg(side)
asc <- iconv(str, "latin1", "ASCII")
ind <- is.na(asc) | asc != str
if (any(ind))
width <- width + nchar(str, "bytes") - nchar(str, "width")
switch(side, left = sprintf("%-*s", width, str),
right = sprintf("%*s", width, str),
both = sprintf("%-*s", width, sprintf("%*s", floor(width/2), str)))
}
lapply(c("ZZZ", "ZZZZZZ", "ЯЯЯ", "ЯЯЯЯЯЯ"),
function(x) paste0(str_pad(x, 20), ": VALUE"))
#> [[1]]
#> [1] "ZZZ : VALUE"
#>
#> [[2]]
#> [1] "ZZZZZZ : VALUE"
#>
#> [[3]]
#> [1] "ЯЯЯ : VALUE"
#>
#> [[4]]
#> [1] "ЯЯЯЯЯЯ : VALUE"
#>