On 27/02/2010 12:43 AM, xlr82sas wrote:
Hi,
If I do the following
sprintf("%A",pi)
"0X1.921FB54442D18"
I have this 16 byte character string
hx<-"400921FB54442D18"
This is the exact hex16 representation of PI in
IEEE float that R uses in Intel 32bit(little endian) Windows
SAS uses the same representation. 11 bit exponent and 53 bit mantissa.
I want to do is recreate the float exactly from the 16 char hex
something like
MyPI<-readChar(hx,numeric(),16)
or in SAS
MyPI=input("400921FB54442D18",hex16.);
put MyPI=;
MYPI=3.1415926536
What I am trying to do is set up a lossless
transfer method from SAS to R
The way I would do it is to convert the hx string to raw bytes, then
read the raw bytes as a binary value. I think this works for one
string; it would need some work to handle more than one:
hexdigits <- function(s) {
digits <- 0:15
names(digits) <- c(0:9, LETTERS[1:6])
digits[strsplit(s, "")[[1]]]
}
bytes <- function(s) {
digits <- matrix(hexdigits(s), ncol=2, byrow=TRUE)
as.raw(digits %*% c(16,1))
}
todouble <- function(bytes) {
con <- rawConnection(bytes)
val <- readBin(con, "double", endian="big")
close(con)
val
}
todouble(bytes("400921FB54442D18"))
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