R help - Dec 2008 - Replacing tabs with appropriate number of spaces

Colleagues,

Platform: OS X (but issue applies to all platforms)
Version: 2.8.0

I have a mixture of text and data that I am outputting via R to a pdf  
document (using a fixed-width font).  The text contains tabs that  
align columns properly with a fixed-width font in a terminal window.   
However, when the PDF document is created, the concept of a tab is not  
invoked properly and columns do not align.

I could use brute force as follows:
1.  identify lines of text containing tabs
2.  strsplit on tabs
3.  count characters preceding the tab, then replace the tab with the  
appropriate number of spaces (e.g., if the string preceding the tab  
has 29 characters, add 3 spaces), then paste(..., sep="")

However, I am sure a more elegant approach exists.  Can anyone offer  
one?

Dennis


Dennis Fisher MD
P < (The "P Less Than" Company)
Phone: 1-866-PLessThan (1-866-753-7784)
Fax: 1-415-564-2220
www.PLessThan.com

On Tue, Dec 9, 2008 at 10:39 AM, Dennis Fisher <fisher at plessthan.com>
wrote:
> Colleagues,
>
> Platform: OS X (but issue applies to all platforms)
> Version: 2.8.0
>
> I have a mixture of text and data that I am outputting via R to a pdf
> document (using a fixed-width font).  The text contains tabs that align
> columns properly with a fixed-width font in a terminal window.  However,
> when the PDF document is created, the concept of a tab is not invoked
> properly and columns do not align.
>
> I could use brute force as follows:
> 1.  identify lines of text containing tabs
> 2.  strsplit on tabs
> 3.  count characters preceding the tab, then replace the tab with the
> appropriate number of spaces (e.g., if the string preceding the tab has 29
> characters, add 3 spaces), then paste(..., sep="")
Tabs usually just expand to a fixed number of spaces - so
gsub("\t","
  ", text) would do the job.

Hadley

-- 
http://had.co.nz/

This is basically your approach, but automated a bit more than you describe:


library(gsubfn)

tmp <-
strsplit('one\ttwo\nthree\tfour\n12345678\t910\na\tbc\tdef\tghi\n','\n')[[1]]

tmp2 <- gsubfn('([^\t]+)\t', function(x) {
  ln <- nchar(x)
  nsp <- 8-(ln %% 8)
  sp <- paste( rep(' ', nsp), collapse='' )
  paste(x,sp, sep='')
}, tmp )

tmp2
cat(tmp2, sep='\n')

This is based on the assumption of tab stops every 8 columns, change the 2
8's above if you want something different.

Hope this helps,


--
Gregory (Greg) L. Snow Ph.D.
Statistical Data Center
Intermountain Healthcare
greg.snow at imail.org
801.408.8111

> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> project.org] On Behalf Of Dennis Fisher
> Sent: Tuesday, December 09, 2008 9:40 AM
> To: r-help at stat.math.ethz.ch
> Subject: [R] Replacing tabs with appropriate number of spaces
>
> Colleagues,
>
> Platform: OS X (but issue applies to all platforms)
> Version: 2.8.0
>
> I have a mixture of text and data that I am outputting via R to a pdf
> document (using a fixed-width font).  The text contains tabs that
> align columns properly with a fixed-width font in a terminal window.
> However, when the PDF document is created, the concept of a tab is not
> invoked properly and columns do not align.
>
> I could use brute force as follows:
> 1.  identify lines of text containing tabs
> 2.  strsplit on tabs
> 3.  count characters preceding the tab, then replace the tab with the
> appropriate number of spaces (e.g., if the string preceding the tab
> has 29 characters, add 3 spaces), then paste(..., sep="")
>
> However, I am sure a more elegant approach exists.  Can anyone offer
> one?
>
> Dennis
>
>
> Dennis Fisher MD
> P < (The "P Less Than" Company)
> Phone: 1-866-PLessThan (1-866-753-7784)
> Fax: 1-415-564-2220
> www.PLessThan.com
>
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