| Re: Forcing READ_ASCII output to be a set of strings... [message #43143 is a reply to message #43004] |
Mon, 14 March 2005 13:34   |
Jonathan Greenberg
Messages: 91
Registered: November 2002
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Member |
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I actually kicked a backwards compatible version of this to the IDL help,
and also uploaded it to the RSI user contrib website. You are right, I
probably should have renamed the file (we'll see if IDL bounces the upload
and asks me to rename it), but here are the mods I made to the "official"
read_ascii release:
***
Function call mod:
function read_ascii_string, $
file, $ ; IN:
RECORD_START=recordStart, $ ; IN: (opt)
NUM_RECORDS=numRecords, $ ; IN: (opt)
TEMPLATE=template, $ ; IN: (opt)
DATA_START=dataStart, $ ; IN: (opt)
DELIMITER=delimiter, $ ; IN: (opt)
MISSING_VALUE=missingValue, $ ; IN: (opt)
COMMENT_SYMBOL=commentSymbol, $ ; IN: (opt)
; FIELDS=fields, $ ; IN: (opt) [not implemented]
VERBOSE=verbose, $ ; IN: (opt)
HEADER=header, $ ; OUT: (opt)
COUNT=count, $ ; OUT: (opt)
; **** JONATHAN'S MOD ****
DATA_TYPE=data_type ; IDL data type (opt)
Modifying the default data_type without needing to use a template:
; Keeps the default to floating point
if n_elements(data_type) eq 0 then data_type=4
fieldTypesUse = REPLICATE(data_type, fieldCountUse)
***
This would cause zero problems, as far as I can tell, if a user just swapped
this in (you'll note that I kept the default a floating point).
The reason I didn't want to use a template was I didn't see a quick way to
make it apply a string format to an arbitrarily long ascii file (e.g. If I
add a new column to my DB, don't I have to modify the ascii template each
time?)
The reason I thought this would be better as a text default is that you can
easily go from string -> number, but you can't go backwards. Considering
the input is text, why would they just assume it is filled with floating
point numbers? It appears to be completely arbitrary... A string format
appears to be the most "generalized" form you could use.
--j
On 3/14/05 12:51 PM, in article 113bua0b4hdv2a2@corp.supernews.com, "Michael
Wallace" <mwallace.no.spam@no.spam.swri.edu.invalid> wrote:
> Jonathan Greenberg wrote:
>> I kinda answered my own question -- I took the read_ascii.pro that IDL
>> distributes and simply changed the default behavior on this line:
>>
>> fieldTypesUse = REPLICATE(4L, fieldCountUse)
>>
>> To
>>
>> fieldTypesUse = REPLICATE(7L, fieldCountUse)
>>
>> This appears to work fine... I'm kicking IDL a request to modify this so
>> it'll default to a user-defined format...
>>
>
> Um, this is dangerous. First, if you ever want to distribute this
> application, or at least give it to someone else, you'll have to make
> the same modification in their IDL install. It can be *very* problematic.
>
> Second, why should the default be string rather than float? Just
> because you have a need to use strings for this particular application
> doesn't mean that RSI should change their defaults. For default values,
> a floating point number is the best assumption to make. If the default
> values don't work for you, use a template. This is why templates exist...
>
> -Mike
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