通过填充空格到指定长度来居中字符串 [英] center a string by padding spaces up to a specified length

问题描述

我有一个名字矢量，像这样:

I have a vector of names, like this:

x <- c("Marco", "John", "Jonathan")

我需要对其进行格式化，以便通过添加前导和尾随空格来使名称集中在10个字符的字符串中:

I need to format it so that the names get centered in 10-character strings, by adding leading and trailing spaces:

> output
# [1] "  Marco   " "   John    " " Jonathan "

我希望解决方案比使用paste，rep和计算nchar复杂吗? (也许使用sprintf，但我不知道如何操作.)

I was hoping a solution less complicated than to go with paste, rep, and counting nchar? (maybe with sprintf but I don't know how).

推荐答案

这是一个sprintf()解决方案，它使用简单的辅助矢量f确定低边宽度.然后，我们可以使用*字符将宽度插入到我们的格式中，并使用右侧的ceiling()来计算名称中的奇数个字符.由于我们的最大字符宽度为10，因此每个超过10个字符的名称都将保持不变，因为我们使用pmax()调整了这些宽度.

Here's a sprintf() solution that uses a simple helper vector f to determine the low side widths. We can then insert the widths into our format using the * character, taking the ceiling() on the right side to account for an odd number of characters in a name. Since our max character width is at 10, each name that exceeds 10 characters will remain unchanged because we adjust those widths with pmax().

f <- pmax((10 - nchar(x)) / 2, 0)

sprintf("%-*s%s%*s", f, "", x, ceiling(f), "")
# [1] "  Marco   "  "   John   "  " Jonathan "  "Christopher"

数据:

x <- c("Marco", "John", "Jonathan", "Christopher")

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