On 12-03-25 10:45 AM, Marc Schwartz wrote:
On Mar 25, 2012, at 7:14 AM, Duncan Murdoch wrote:
On 12-03-24 10:47 PM, J Toll wrote:
On Sat, Mar 24, 2012 at 7:30 PM, Duncan Murdoch
<murdoch.dun...@gmail.com> wrote:
Do we have a format that always includes a decimal point and a given number
of significant digits, but otherwise drops unnecessary characters? For
example, if I wanted 5 digits, I'd want the following:
Round to 5 digits:
1.234567 -> "1.2346"
Drop unnecessary zeros:
1.23 -> "1.23"
Force inclusion of a decimal point:
1 -> "1."
Duncan,
Maybe sprintf() will work for you. As it's a wrapper for C sprintf,
it should have its functionality.
Maybe, but with which format string?
Duncan Murdoch
I don't believe (though could be wrong), that you can do it all with one format string,
but can do it conditionally based upon the input. According to the C printf
documentation, the use of "#" forces a decimal point to be present, even if
there are no trailing digits. Thus:
sprintf("%#.f", 1)
[1] "1."
The other two values seem to be handled by signif() when applied to each value
individually:
signif(1.234567, 5)
[1] 1.2346
signif(1.23, 5)
[1] 1.23
But, not when a vector:
signif(c(1.234567, 1.23), 5)
[1] 1.2346 1.2300
So, wrapping that inside a function, using ifelse() to test for an integer
value:
signif.d<- function(x, digits)
{
ifelse(x == round(x),
sprintf("%.#f", x),
signif(x, digits))
}
x<- c(1.234567, 1.23, 1)
signif.d(x, 5)
[1] "1.2346" "1.23" "1."
signif.d(x, 6)
[1] "1.23457" "1.23" "1."
signif.d(x, 7)
[1] "1.234567" "1.23" "1."
Not extensively tested of course, but hopefully that might work for your needs
Duncan.
Thanks. I had put together a different conditional (just do the
conversion, then add a decimal point at the end if none is seen), but I
was surprised that there was no standard format for this.
In case anyone is interested, I want to output code in a language (GLSL)
that sees 1 and 1. as different types. I want a floating point value,
so I need the decimal point.
Duncan Murdoch
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
