| byteoder for float numbers conversion [message #8071] |
Tue, 04 February 1997 00:00  |
yafeng
Messages: 4
Registered: December 1995
|
Junior Member |
|
|
I want to convert the float numbers from UNIX format(big-edian)
to PC format(small-edian). For example, I have a float array
data(420)
None of these commands worked:
byteorder, data
byteorder, data, /xdrtof
byteorder, data, /ftoxdrt
I can write the C program to do it but my file is the IDL
structure so I like to solve this problem in IDL too.
Thanks.
P.S: Does anybody has the IDL program drawing topographic
map for EEG(ERP) data? Thanks a lot.
Yafeng Li
|
|
|
|
| Re: byteoder for float numbers conversion [message #8136 is a reply to message #8071] |
Thu, 06 February 1997 00:00  |
Thomas A. McGlynn
Messages: 23
Registered: March 1996
|
Junior Member |
|
|
Peter Suetterlin wrote:
>
> In article <5d8mo8$n98@elaine44.stanford.edu>,
> yafeng@leland.Stanford.EDU (Meili Zhong) writes:
>
>> I want to convert the float numbers from UNIX format(big-edian)
>> to PC format(small-edian). For example, I have a float array
>> data(420)
>
> byteorder, data, /lswap
>
> Or have a look at the /XDR Keyword for opening files.
>
> Peter
>
> Peter "Pit" Suetterlin
I've had lots of problems with the byteorder routine. It's
been broken on a number of versions of IDL on Dec hardware
and some PC versions.
If you actually know that you just want to invert data of
a given type you can do things like:
float x[100];
qinvers = float(rotate(byte(x,0,4,100),5),0,100)
to invert bytes. You can look at the IDL astronomy library
rotines host_to_ieee and ieee_to_host at
http://idlastro.gsfc.nasa.gov/ftp/pro/misc
to see if any machines/IDL versions you're interested in have
errors in their byteorder implementations. There do
seem to be some problems indicated for linux and Windows
versions of IDL. These routines try to take care of these little
gotcha's in a generic way.
Good luck,
Tom McGlynn
tam@silk.gsfc.nasa.gov
|
|
|
|
| Re: byteoder for float numbers conversion [message #8216 is a reply to message #8071] |
Tue, 18 February 1997 00:00 |
Liam Gumley
Messages: 473
Registered: November 1994
|
Senior Member |
|
|
William Connolley wrote:
> In article n98@elaine44.Stanford.EDU, yafeng@leland.Stanford.EDU (Meili Zhong) writes:
>> I want to convert the float numbers from UNIX format(big-edian)
>> to PC format(small-edian).
>> None of these commands worked:
>> byteorder, data
>> byteorder, data, /xdrtof
>> byteorder, data, /ftoxdrt
> To go from SUN-floating-point to DECalpha-floating-point I use
> byteorder,data,/lswap
SWAP_ENDIAN works for me, e.g.
data = swap_endian( temporary( data ) )
It handles floating point as well as integer types.
Cheers,
Liam.
|
|
|
|
| Re: byteoder for float numbers conversion [message #8221 is a reply to message #8071] |
Tue, 18 February 1997 00:00 |
pit
Messages: 92
Registered: January 1996
|
Member |
|
|
In article <5ebvgk$k1d@kwuz.nerc-keyworth.ac.uk>,
wmc@bsfiles.nerc-bas.ac.uk (William Connolley) writes:
>> I want to convert the float numbers from UNIX format(big-edian)
>> to PC format(small-edian).
> To go from SUN-floating-point to DECalpha-floating-point I use
> byteorder,data,/lswap
>
> It might work for you in this case.
> xdr doesn't sound right to me.
Why not? Of course you also have to write the data using /XDR.
This is the easiest way to keep code *and* data platform-independent.
> ps - PCs are the spawn of the devil. Why not leave your data on unix
> where it will be happy? ;-)
You're mixing things up. Little Endian is a *hardware* thing. It has
nothing to do with the OS you are running. IDL for Linux is still LE.
We have a mixed cluster here (SunOS, HP-UX, Linux), all Unix. Still
there is the Big/Little Endian problem.
Peter
--
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~
Peter "Pit" Suetterlin http://www.uni-sw.gwdg.de/~pit
Universitaets-Sternwarte Goettingen
Tel.: +49 551 39-5048 pit@uni-sw.gwdg.de
-- * -- * ...-- * -- * ...-- * -- * ...-- * -- * ...-- * -- * ...-- * --
Come and see the stars! http://www.kis.uni-freiburg.de/~ps/SFB
Sternfreunde Breisgau e.V. Tel.: +49 7641 3492
____________________________________________________________ ______________
|
|
|
|
| Re: byteoder for float numbers conversion [message #8224 is a reply to message #8071] |
Tue, 18 February 1997 00:00 |
wmc
Messages: 117
Registered: February 1995
|
Senior Member |
|
|
In article n98@elaine44.Stanford.EDU, yafeng@leland.Stanford.EDU (Meili Zhong) writes:
> I want to convert the float numbers from UNIX format(big-edian)
> to PC format(small-edian).
> None of these commands worked:
> byteorder, data
> byteorder, data, /xdrtof
> byteorder, data, /ftoxdrt
To go from SUN-floating-point to DECalpha-floating-point I use
byteorder,data,/lswap
It might work for you in this case.
xdr doesn't sound right to me.
ps - PCs are the spawn of the devil. Why not leave your data on unix where
it will be happy? ;-)
---
William M Connolley | wmc@bas.ac.uk | http://www.nbs.ac.uk/public/icd/wmc/
Climate Modeller, British Antarctic Survey | Disclaimer: I speak for myself
|
|
|
|
comp.lang.idl-pvwave archive
Members
Search
Help
Login
Home
