On Jan 24, 11:18 pm, Matt Francis <mattjamesfran...@gmail.com> wrote:
> I have a data structure with many tags, and an array of these
> structures holding a bunch of data.
>
> Many of the tags will often not be present or relevant in some
> particular context, and so will be just zeros for the whole array. I
> want to be able to selectively write out to file just those tage that
> contain usefull data.
>
> I have a line like this for the case that I want to write out all the
> tags:
>
> for i=0l,n_elements(foo)-1 do $
> printf,lunw,foo[i], format=FMT
>
> If however I want to write out not all of the tags, I'm not sure how
> to do this? I can create an appropriate FMT string for the subset of
> tags, and could do something like:
>
> for i=0l,n_elements(foo)-1 do $
> printf,lunw,foo[i].tag1,foo[i].tag2, format=FMT
>
> where I list just those tags I want written out. This hard codes what
> tags to write though. Since there are many possible combinations of
> which ones I want written out, I'd need dozens of IF/THEN lines like
>
> if (want tags 1 and 2) then begin
> for i=0l,n_elements(foo)-1 do $
> printf,lunw,foo[i].tag1,foo[i].tag2, format=FMT'
> endif else if (want tags 1 and 3 ) then begin
> for i=0l,n_elements(foo)-1 do $
> printf,lunw,foo[i].tag1,foo[i].tag3, format=FMT'
> endelse
>
> This is clearly not the solution. I can easily create an array
> indicating the tags I want written out and would love to be able to
> simply use the command:
>
> for i=0l,n_elements(foo)-1 do $
> printf,lunw,foo[i].(indx), format=FMT
>
> but IDL (at least my V7.1) does not allow this kind of indexing. Tags
> can only be directly indexed, not via arrays of indices.
>
> I could do something like
>
> for i=0l,n_elements(foo)-1 do begin
> for j=0,ntags-1 do begin
> printf,lunw,foo[i].(indx[j])
> endfor
> endfor
>
> however this creates a newline for each printf statement, and I need
> all the data for each array element on one line.
>
> Any ideas?
How about using something like that last case to construct a string,
and then print it out at the end of the outer for loop
for i=0l,n-1 do begin
str=''
for j=0,ntags-1 do begin
prints, str, foo[i].(indx[j])
endfor
printf, lunw, str
endfor
-Jeremy.
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