[R] Max sig figs as well as Min in print?

[Prof Brian Ripley]

On Thu, 5 Jun 2003 Ted.Harding at nessie.mcc.ac.uk wrote:

> Hi Folks,
> 
> Consider the following example (artificial, but it illustates the point):
> 
>   > r2<-sqrt(2)
>   > x<-2-r2*r2
> 
>   > print(c(pi,sqrt(pi)),digits=5)
>   [1] 3.1416 1.7725
> 
> 
>   > print(c(pi,sqrt(pi),x),digits=5)
>   [1]  3.1416e+00  1.7725e+00 -4.4409e-16
> 
> whereas I would prefer
> 
>   [1] 3.1416 1.7725 0.0000
> 
> which could be achieved by
> 
>   > print(c(pi,sqrt(pi),round(x)),digits=5)
>   [1] 3.1416 1.7725 0.0000
> 
> if need be.
> 
> The above of course is due to the definition of "digits" as the miniumum
> number of significant figures to print. In order to avoid the behaviour of
> the second "print" and make it like the last line, one would need to be
> able to set somthing like "maxdigits=5" as well as "digits=5".
> 
> Is anything of this sort possible (apart from anticipating the situation
> and wrapping relevant computations in "round")?

Might zapsmall help?

> print(zapsmall(c(pi,sqrt(pi),x)), digits=5)
[1] 3.1416 1.7725 0.0000

Alternatively, 

sprintf("%8.4f %8.4f %8.4f", pi,sqrt(pi),x)
formatC(c(pi,sqrt(pi),x), digits=4, format="f")


-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595