| Re: Huge datasets under Win2000 [message #25665 is a reply to message #25664] |
Wed, 04 July 2001 11:51   |
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david[2]
Messages: 100
Registered: June 2001
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Senior Member |
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Joe Means writes:
> have to read in over 13,000,000 observations [eventually over
> 33,000,000] with the structure
> dataShort = {dataShort, returnNum:0L, x:0D,y:0D,z:0D}
>
> At first, either when reading in or processing, I ran out of memory with
> a message about IDL not being able to allocate memory to make the
> array. So I read this into an Assoc variable which works fine. Now ,
> however, when I try to access parts of this data [dataS is the
> Associated structure array]:
> datSvX = (dataS.y-yll)/cellsize
> I get the error:
> % File expression not allowed in this context: DATAS.
Joe, sorry. I was distracted this morning what with
playing tennis and watching that Henman/Federer match
at Wimbledon. In fact, I don't know why in the world
I was even reading the IDL newsgroup! :-(
But I don't think this error has anything at all to
do with reading large data sizes. I think it has to
do with the way you are accessing the associated
variable. (Although I admit I've never seen the
error message before.)
If I understand your message correctly, DATAS is the
associated variable. Is this right?
dummy = {dataShort, returnNum:0L, x:0D,y:0D,z:0D}
OpenU, lun, 'mydatafile.dat', /Get_Lun
datas = Assoc(lun, {dataShort})
It is really incorrect to think of this as an
array of structures, which I think is what you may
be doing. In other words, this syntax doesn't work
with associated variables:
b = datas(4:6)
With associated variables, you are going to have
to pull each structure out to work with it:
struct1 = datas(5)
struct1.x = 5.5
datas(5) = struct1
I can't really tell what you are doing with this
syntax:
datSvX = (dataS.y-yll)/cellsize
But, I'm pretty sure this is the source of your
error.
Cheers,
David
--
David Fanning, Ph.D.
Fanning Software Consulting
Phone: 970-221-0438 E-Mail: davidf@dfanning.com
Coyote's Guide to IDL Programming: http://www.dfanning.com/
Toll-Free IDL Book Orders: 1-888-461-0155
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