| READ_ASCII - accessing data from structures [message #39371] |
Wed, 12 May 2004 10:14  |
m.doyle
Messages: 6
Registered: January 2004
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Junior Member |
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Hello all,
I wonder if anyone might be able to help me with this?
I'm using the IDL READ_ASCII function to read in a semicolon seperated
file, after which I'd like to access individual elements of that data
file. From the RSI website, I see that I can access the data fields
(i.e. each column of data) by using, for example;
print, mydata.(4)
using the Variable_Name.(Tag_Index) method.
Could someone tell me how to get to the individual elements of
mydata.(4)?? Using the above I can only get a large stream of numbers,
I need to use them one by one.
Many thanks for your help!
Martin
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| Re: read_ascii [message #41755 is a reply to message #39371] |
Wed, 08 December 2004 12:54  |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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Francois writes:
> I use the following code to read an ascii file:
>> filename = dialog_pickfile(path='c:\')
>> data = READ_ASCII(filename, DATA_START=1, DELIMITER= ',')
>> data = data.field1
>
> I want data to become an array instead of a structure.
>
> The problem is that sometimes the array is contained in field01,
> sometimes in field01.
> How come it varies ?
I'm not sure I see the variation in the question,
but in any case I don't know why it varies. If it
*is* varying, why not try this:
data = READ_ASCII(filename, DATA_START=1, DELIMITER= ',')
data = data.(0)
Cheers,
David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.dfanning.com/
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| Re: read_ascii [message #41992 is a reply to message #41754] |
Thu, 09 December 2004 05:52 |
Benjamin Tupper
Messages: 1
Registered: December 2004
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Junior Member |
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Rick Towler wrote:
>
>> The problem is that sometimes the array is contained in field01,
>> sometimes in field01.
>
>
>> How come it varies ?
>
>
> You mean "field1" and "field01".
>
> When confronted with less than 10 fields, READ_ASCII will return
> field1-field9, when you have more than 10, field01-field99.
>
> It is unfortunate that READ_ASCII behaves this way but David's
> suggestion of addressing the structure by tag index instead of tag name
> will solve your problem.
>
Hi,
You could define the names of the fields using ASCII_TEMPLATE before
calling READ_ASCII. You can define the template without using
ASCII_TEMPLATE - a little study of the structure returned by
ASCII_TEMPLATE should help.
Alternatively, you could modify READ_ASCII (call it something else,
though, like MY_READ_ASCII). You can force the routine to always use N
digits in the field names by modifying the following line (line 874 in
my version) ....
digits_str = $
strtrim(string(strlen(strtrim(string(fieldCountUse),2))),2)
to something like this...
my_dig_len = fieldCountUse > 2
digits_str = $
strtrim(string(strlen(strtrim(string(my_dig_len),2))),2)
On a related note, I have drifted away from treating columnated ASCII
data files as nColumns of vectors. Instead, I treat them as vectors of
structures where each row is a record and each column is a field of the
record. This works fine for flatly organized data and I find a vector
of structures MUCH easier to manage in IDL than a structure of vectors.
If you are interested seeing my version of READ_ASCII then shoot me an
email.
Cheers,
Ben
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