[R] string syntactic sugar in R? - long post

(Ted Harding) Ted.Harding at nessie.mcc.ac.uk
Sat May 7 12:26:39 CEST 2005

On 07-May-05 James Bullard wrote:
> The other thing to use is 'sprintf', which would be fantastic in R if
> it imputed types based on the format string.
> As it is now, for your query you would do:
>> sprintf("SELECT %s FROM table WHERE date = '%s'", "column",
>> "2005-10-12")
> [1] "SELECT column FROM table WHERE date = '2005-10-12'"
> Which, in my opinion is nicer than the corresponding paste, and about
> as nice as gstring. The issue that I always have with sprintf is when I
> use numbers, specifically integers. As the function is just a wrapper
> for the C function  and because numbers are implicitly doubles the
> following doesnt work:
>>  sprintf("SELECT %s FROM table WHERE age = %d", "column", 1)
> Error in sprintf("SELECT %s FROM table WHERE age = %d", "column", 1) : 
>         use format %f, %e or %g for numeric objects
> It does work however if you do
>> sprintf("SELECT %s FROM table WHERE age = %d", "column",
>> as.integer(1))
> [1] "SELECT column FROM table WHERE age = 1"
> This however, is not so nice - are there reasons why this has to be
> like this? This might be naive but I would think it would be pretty
> simple in R to do this automatically. Thanks for any insight. 

You can force integer format using %f if you use it as "%.0f":

  sprintf("SELECT %s FROM table WHERE age = %.0f", "column", 1)
  ## [1] "SELECT column FROM table WHERE age = 1"

The rule (as in C) is that "%a.bf" outputs a format for the
floating-point number in a minimum width of 'a' characters
("field width", left-padded with space), with 'b' digits following
the decimal point (and no decimal point is printed if b=0);
if either 'a' or 'b' is missing then no corresponding restriction
is imposed.

Best wishes,

E-Mail: (Ted Harding) <Ted.Harding at nessie.mcc.ac.uk>
Fax-to-email: +44 (0)870 094 0861
Date: 07-May-05                                       Time: 11:05:06
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