| Re: undefining structures ? [message #1564] |
Fri, 17 December 1993 08:24 |
rudy
Messages: 2
Registered: April 1993
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Junior Member |
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> I am trying to read in files of a priori undefined organization within IDL.
>
> The files are "tabular" binary files (an a priori unknown number of columns
> of an a priori unknown type with an a priori unknown number of rows).
> "a priori unknown" means documented in a file header.
... and so on
I had a similar problem with some data and I solved it with a .pro I've
included at the end of this message. It creates the structure by actually
writing a .pro in the current directory and compiling this .pro; so you must
have rw priveleges. It has a switch which allows you to delete the .pro, but
after running this create_struct.pro many times, you get quite a few
structures in your IDL session! I've never had a problem with this, although
I don't think I ever got past 100 structures in one IDL session (never tried).
I got it from IDL Astronomy User's library. I deserve no credit for this .pro,
aside from the fact that I found it while net.surfing. I hope it proves
useful.
Don
*********************************
donald.rudy@mve.aero.org
*********************************
pro create_struct, struct, strname, tagnames, tag_descript, DIMEN = dimen, $
CHATTER = chatter, NODELETE = nodelete
;+
; NAME:
; CREATE_STRUCT
; PURPOSE:
; Dynamically create an IDL structure variable from list of tag names
; and data types of arbitrary dimensions. Useful when the type of
; structure needed is not known until run time.
; CALLING SEQUENCE:
; CREATE_STRUCT, STRUCT, strname, tagnames, tag_descript, DIMEN = ,
; CHATTER= , NODELETE =
; INPUTS:
; STRNAME - name to be associated with structure (string)
; Must be unique for each structure created. Set
; STRNAME = '' to create an anonymous structure
; TAGNAMES - tag names for structure elements
; (string or string array)
; TAG_DESCRIPT - String descriptor for the structure, containing the
; tag type and dimensions. (e.g., 'A(2),F(3),I', will be
; the descriptor for a structure with 3 tags, strarr(2),
; fltarr(3) and Integer scalar, respectively.
; Allowed types are 'A' for strings, 'B' for unsigned byte
; integers, 'I' for integers, 'L' for longword integers,
; 'F' for floating point, 'D' for double precision
;
; OPTIONAL INPUTS:
; DIMEN - number of dimensions of structure array (default is 1)
; CHATTER - If /CHATTER is set, then CREATE_STRUCT will display
; the dimensions of the structure to be created, and prompt
; the user whether to continue. Default is no prompt.
; NODELETE - If /NODELETE is set, then the temporary file created
; CREATE_STRUCT will not be deleted upon exiting. See below
; OUTPUTS:
; STRUCT - IDL structure, created according to specifications
;
; EXAMPLES:
; IDL> create_struct, new, 'name',['tag1','tag2','tag3'], 'D(2),F,A(1)'
;
; will create a structure variable new, with structure NAME
;
; To see the structure of new:
;
; IDL> help,new,/struc
; ** Structure NAME, 3 tags, 20 length:
; TAG1 DOUBLE Array(2)
; TAG2 FLOAT 0.0
; TAG3 STRING Array(1)
;
; PROCEDURE:
; Generates a temporary procedure file using input information with
; the desired structure data types and dimensions hard-coded.
; This file is then executed with CALL_PROCEDURE.
;
; NOTES:
; A temporary .pro file is created to define structure in the default
; directory, so writing privileges are required. CREATE_STRUCT will
; abort with an information messages if a file already exists with the
; name temp_"strname".pro
;
; At present, can fail if a tag_name cannot be used as a proper
; structure component definition, e.g., '0.10' will not
; work, but a typical string like 'RA' or 'DEC' will.
; A partial workaround checks for characters '\' and '/'
; and '.' and converts them to '_'. in a tag_name.
;
; For more information about structures, see IDL Users' Guide,
; Chapter 8
; RESTRICTIONS:
; *** The name of the structure must be unique, for each structure created.
; Otherwise, the new variable will have the same structure as the
; previous definition (because the temporary procedure will not be
; recompiled). No error message will be generated ***
;
; SUBROUTINES CALLED:
; function gettok, function repchr
;
; MODIFICATION HISTORY:
; Version 1.0 RAS January 1992
; Modified 26 Feb 1992 for Rosat IDL Library (GAR)
; Modified Jun 1992 to accept arrays for tag elements -- KLV, Hughes STX
; Accept anonymous structures W. Landsman HSTX Sep. 92
;-
;----------------------------------------------------------- --------------------
npar = N_params()
if (npar LT 4) then begin
print,'Syntax - CREATE_STRUCT, STRUCT, strname, tagnames, tag_descript,
print,' DIMEN = dimen, chatter=chatter (0)'
return
endif
if (N_elements(chatter) eq 0) then chatter = 1 ;default is 1
if (N_elements(dimen) eq 0) then dimen = 1 ;default is 1
if (dimen lt 1) then begin
print,' Number of dimensions must be >= 1. Returning.'
return
endif
; For anonymous structure, strname = ''
anonymous = 0b
if (strlen( strtrim(strname,2)) EQ 0 ) then anonymous = 1b
; --- Determine if a file already exists with same name as temporary file
tempfile = 'temp_' + strname
list = findfile( tempfile + '.pro', COUNT = Nfile)
if (Nfile GT 0) then begin
print,' Temporary file '+tempfile+' found. Returning.'
return
endif
;
;
good_fmts = [ 'A', 'B', 'I', 'L', 'F', 'D' ]
fmts = ["' '",'0B','0','0L','0.0','0.0D0']
arrs = [ 'strarr', 'bytarr', 'intarr', 'lonarr', 'fltarr', 'dblarr']
ngoodf = N_elements(good_fmts)
;
; If tagname is a scalar string separated by commas, convert to a string array
tagname = tagnames
sz_name = size( tagnames )
if ( sz_name(0) Eq 0 ) then begin
tempname = tagnames
tagname = gettok(tempname,',')
while (tempname NE '') do tagname = [ tagname, gettok(tempname,',') ]
endif else tagname = tagnames
Ntags = N_elements(tagname)
; Replace any illegal characters in the tag names with an underscore
bad_chars = [ '\', '/', '.']
for k = 0, N_elements( bad_chars) -1 do $
tagname = repchr( tagname, bad_chars(k), '_' )
; If user supplied a scalar string descriptor then we want to break it up
; into individual items. This is somewhat complicated because the string
; delimiter is not always a comma, e.g. if 'F,F(2,2),I(2)', so we need
; to check positions of parenthesis also.
;
sz = size(tag_descript)
if sz(0) EQ 0 then begin
tagvar = strarr( Ntags)
temptag = tag_descript
for i = 0, Ntags - 1 do begin
comma = strpos( temptag, ',' )
lparen = strpos( temptag, '(' )
rparen = strpos( temptag, ')' )
if ( comma GT lparen ) and (comma LT Rparen) then pos = Rparen+1 $
else pos = comma
if pos EQ -1 then begin
if i NE Ntags-1 then message, $
'WARNING - could only parse' + strtrim(i+1,2) + 'string descriptors'
tagvar(i) = temptag
goto, DONE
endif else begin
tagvar(i) = strmid( temptag, 0, pos )
temptag = strmid( temptag, pos+1, 120)
endelse
endfor
DONE:
endif else tagvar = tag_descript
; Break up the tag descriptor into a format and a dimensoin
tagfmts = strmid( tagvar, 0, 1)
tagdim = strtrim( strmid( tagvar, 1, 80),2)
;
; create string array for IDL statements, to be written into
; 'temp_'+strname+'.pro'
;
pro_string = strarr (ntags + 2)
;
if (dimen EQ 1) then begin
pro_string(0) = "struct = { " + strname + " $"
pro_string(ntags+1) = " } "
endif else begin
dimen = fix(dimen)
pro_string(0) = "struct " + " = replicate ( { " + strname + " $"
pro_string(ntags+1) = " } , " + string(dimen) + ")"
endelse
for i = 0, ntags-1 do begin
goodpos = -1
try = strupcase( tagfmts(i) )
for j = 0,ngoodf-1 do $
if ( strpos( try,good_fmts(j)) ge 0 ) then goodpos = j
if ( goodpos LT 0) then begin
print,' Format not recognized: ' + tagfmts(i)
print,' Allowed formats are :',good_fmts
stop,' Redefine tag format (' + string(i) + ' ) or quit now'
endif else $
if (tagdim(i) EQ '') then fmt = fmts(goodpos) else $
fmt = arrs(goodpos) + tagdim(i)
if anonymous and ( i EQ 0 ) then comma = '' else comma = " , "
pro_string(i+1) = comma + tagname(i) + ": " +fmt + " $"
endfor
; Check that this structure definition is OK (if chatter set to 1)
if keyword_set ( Chatter ) then begin
ans = ''
print,' Structure ',strname,' will be defined according to the following:'
temp = repchr( pro_string, '$', '')
print, temp
read,' OK to continue? (Y or N) ',ans
if strmid(strupcase(ans),0,1) eq 'N' then begin
print,' Returning at user request.'
return
endif
endif
;
; ---- open temp file and create procedure
;
openw, unit, tempfile +'.pro', /get_lun
printf, unit, 'pro ' + tempfile + ', struct'
for j = 0,N_elements(pro_string)-1 do $
printf, unit, strtrim( pro_string(j) )
printf, unit, 'return'
printf, unit, 'end'
free_lun, unit
;
call_procedure, tempfile, struct
if keyword_set( NODELETE ) then begin
message,'Created temporary file ' + tempfile + '.pro',/INF
return
endif
if ( !version.os EQ 'vms' ) then spawn, 'delete '+ tempfile +'.pro;' else $
spawn, 'rm ' + tempfile + '.pro'
return
end ;pro create_struct
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| Re: undefining structures ? [message #1595 is a reply to message #1564] |
Mon, 06 December 1993 13:35  |
offenbrg
Messages: 31
Registered: August 1993
|
Member |
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lucio@ifctr.mi.cnr.it (Lucio Chiappetti) writes:
Newsgroups: comp.lang.idl-pvwave
Subject: Re: undefining structures ?
Distribution: world
References: <Pine.3.05.9312061924.D19888-c100000@poseidon.ifctr.mi.cnr.it>
lucio@ifctr.mi.cnr.it (Lucio Chiappetti) writes:
> This structure will have a number of members s.keyname corresponding to
> keywords, and a member s.data.
> The member s.data is created as: data:replicate(template,nrows)
> template= {record,TIME:0L, THETA:0L, PHI:0L, ENERGY:0 , undef:0B}
> where the names and types of the tags are constructed by my procedure
> according to information in the file itself. So later I can access the
> individual columns as s.data.time, etc.
Bad news. As far as I know (and if anyone knows better, please let me know),
IDL won't let you do what you're trying to do.
(a) You can't make "template" an anonymous structure because you're using
it as part of another structure.
(b) Once defined within an IDL session, a structure name (like "RECORD")
can't be renamed.
The quick & dirty way out of it, as I see it, is to have each different
version of TEMPLATE have a different structure name (e.g. REC1, REC2, etc).
Another way would be to skip TEMPLATE entirely, and just create one
structure, with s.keyname, s.time, s.theta, etc.
A third way would be to: instead of making DATA a structure, you
make it an array, like an array of strings, and put the data in the array in
a consistent format.
For example, you could create the S structure with 3 words: s.keynames,
s.formats and s.data. Then you'd encode TIME as, say, an 8-digit integer
starting at the fifth character of each line. You'd record the format in
the s.formats array, such as '(4x,i8)'. Then to read it out, you'd say
something like
reads,s.data,time,f=s(where(s.keynames eq 'TIME')).formats
Yeah, its convoluted. But, it would work. And you could easily whip up
a function to do the read statement for you, like
time = readmystruc(s,'TIME')
> PS
> I'm using IDL 2.2.1 (and I'm not likely to update it for the time being)
Unless they've changed this for the just-released IDL 3.5, the version of IDL
doesn't matter.
Hope all of this helps.
Joel
--
Joel D Offenberg | "Aren't you in the position of a life-long
Hughes STX/ UIT Science Team | vegetarian giving us your recipe for steak
offenbrg@fondue.gsfc.nasa.gov | and kidney pie?" - Rumpole of the Bailey
I get paid to stare into space. |
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