R help - Jun 2010 - floating point in single precision

Hello,

is there a possibilty in R to convert numbers (double precision, 64bit) into 
single precision ones (32bit).
I need that for compatibility reasons. Until now I call a C application which 
casts a double to a float.

float precision32(double value) {
  return (float)value;
}

But I want to use a R only method. What can I do?

Kind regards,

Sebastian

On Sun, 27 Jun 2010, Sebastian Gibb wrote:
> Hello,
>
> is there a possibilty in R to convert numbers (double precision, 64bit)
into
> single precision ones (32bit).
> I need that for compatibility reasons. Until now I call a C application
which
> casts a double to a float.
>
> float precision32(double value) {
>  return (float)value;
> }
>
> But I want to use a R only method. What can I do?
?as.single
?writeBin
> Kind regards,
>
> Sebastian
-- 
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

Am Sonntag, 27. Juni 2010, 08:39:10 schrieb Prof Brian
Ripley:
> On Sun, 27 Jun 2010, Sebastian Gibb wrote:
> > Hello,
> > 
> > is there a possibilty in R to convert numbers (double precision,
64bit)
> > into single precision ones (32bit).
> > I need that for compatibility reasons. Until now I call a C
application
> > which casts a double to a float.
> > 
> > float precision32(double value) {
> > 
> >  return (float)value;
> > 
> > }
> > 
> > But I want to use a R only method. What can I do?
> 
> ?as.single
> ?writeBin
Thanks a lot for the hints.
I use the following code now:

### function double2singlePrecision
##  wrapper function for .changePrecision(x, size=4)
##
double2singlePrecision <- function(x) {
  stopifnot(is.double(x));
  return(.changePrecision(x, size=4));
}

### function .changePrecision
##  converts double values to double values in a given precision
##  (only correctly working for cut a higher precision to a lower one; e.g.
##  IEEE 754 double precision to IEEE 754 single precision)
##
.changePrecision <- function(x, size) {
  # create a raw object to avoid direct file access
  virtualCon <- raw();
  # write binary data to raw object and change (mostly cut) precision to size
  # size==4 # 32bit, single precision
  # size==8 # 64bit, double precision
  virtualCon <- writeBin(object=x, con=virtualCon, size=size);
  # re-read data
  x <- readBin(con=virtualCon, what=double(), size=size, n=length(x));
  return(x);
}

Kind regards,

Sebastian