RE: [ncl-talk] Replacing type of dimension within subroutine (in NCL 5.2)

Mary,

Thanks for your help on this issue. I suppose there is some interest in
actually having this functionality (modifying attributes in a
subroutine). For example, we typically 1) load a variable from a file,
2) attach some attributes for geo-referencing, 3) attach some attributes
for labelling, and 4) plot it. The subroutines performing these actions
are at least 100 lines long and perform quite a lot of stuff...

> v = get_var(f,"MYVAR")
> get_grid(v)
> get_meta(v)
> p = plot_var(wks,v,res)

The same code using the workaround would look...

> v = get_var(f,"MYVAR")
> tmp = get_grid(v)
> delete(v)
> v = tmp
> delete(tmp)
> tmp = get_meta(v)
> delete(v)
> v = tmp
> delete(tmp)
> p = plot_var(wks,v,res)

I personally prefer the first - more elegant and readable - version. But
I will leave it to the experts to tell me if modifying meta-data of a
variable within a subroutine is should work or not.

Thanks!
Oli

> -----Original Message-----
> From: Mary Haley [mailto:haley@ucar.edu]
> Sent: Donnerstag, 29. April 2010 14:30
> To: Fuhrer Oliver
> Cc: ncl-talk@ucar.edu
> Subject: Re: Replacing type of dimension within
> subroutine (in NCL 5.2)
>
> Hi Oli,
>
> This does look like a problem, although I'm never quite sure
> what the
> expected behavior is when you try to directly change the
> metadata of a
> variable that is passed in to a function or procedure.
>
> I produced a narrowed down version of your script that
> doesn't require
> a data file, and was able to see that it works with 5.1.1 and
> not 5.2.0.
>
> I tried a function version of "replace_dim" that actually
> makes a copy
> of your variable, and that seems to work. If you have enough memory,
> perhaps you can use this as a work-around?
>
> Unfortunately, you can't just replace your current "var" by calling
> this function. You still have to assign it to a new variable, like I
> did with "newvar".
>
> Meanwhile, I'll see what Dave says about this bug.
>
> undef("replace_dim")
> function replace_dim( var1:numeric )
> local s
> begin
> var2 = var1
> print("replace_dim: start")
> delete(var2&lv_ISBL0)
> var2&lv_ISBL0 = fspan(0.,19.,20)
> print("replace_dim: end")
> return(var2)
> end
>
> begin
> print("main: start")
>
> ; read some data
> ;f = addfile("../data/example/lfff00000000p.grb","r")
> ;var = f->FI_GDS10_ISBL
> var = fspan(1,20,20)
> var!0= "lv_ISBL0"
> var&lv_ISBL0 = ispan(1,20,1)
> printVarSummary(var&lv_ISBL0)
>
> ; replace first named dimension from array of integers to array of
> floats
> if (True) then
> newvar = replace_dim(var)
> printVarSummary(newvar&lv_ISBL0)
> else
> delete(var&lv_ISBL0)
> var&lv_ISBL0 = fspan(0.,19.,20)
> printVarSummary(var&lv_ISBL0)
> end if
>
>
> print("main: end")
>
> end
>
>
> On Apr 29, 2010, at 1:49 AM, <Oliver.Fuhrer@meteoswiss.ch>
> <Oliver.Fuhrer@meteoswiss.ch
> > wrote:
>
> > Hi NCL-team,
> >
> > I think I've stumbled over a bug. Since the introduction of
> NCL 5.2 I
> > get an error message if I change the type of a dimension within a
> > subroutine. If not done within a subroutine (set True to False in
> > example script below) everything works fine. Also, in
> version 5.1 this
> > also worked without problems. It seems that upon returning
> NCL tries
> > to
> > replace the variable of the caller with the temporary
> variable within
> > the subroutine and runs into a type conflict.
> >
> > Cheers,
> > Oli
> >
> > PS. Data file for script can be found here
> >
> https://twiki.cscs.ch/twiki/pub/Main/OliverFuhrerDownloads/lff
> f00000000p
> >
> >
> > ------------ example script ----------------------
> >
> > undef("replace_dim")
> > procedure replace_dim( var:numeric )
> > local s
> > begin
> > print("replace_dim: start")
> > delete(var&lv_ISBL0)
> > var&lv_ISBL0 = fspan(0.,19.,20)
> > print("replace_dim: end")
> > return
> > end
> >
> > begin
> > print("main: start")
> >
> > ; read some data
> > f = addfile("../data/example/lfff00000000p.grb","r")
> > var = f->FI_GDS10_ISBL
> > printVarSummary(var&lv_ISBL0)
> >
> > ; replace first named dimension from array of integers to array of
> > floats
> > if (True) then
> > replace_dim(var)
> > else
> > delete(var&lv_ISBL0)
> > var&lv_ISBL0 = fspan(0.,19.,20)
> > end if
> >
> > printVarSummary(var&lv_ISBL0)
> >
> > print("main: end")
> >
> > end
> >
> >
> > ________________________________________
> >
> > Oliver Fuhrer
> > Numerical Models
> >
> > Federal Departement of Home Affairs FDHA
> > Federal Office of Meteorology and Climatology MeteoSwiss
> >
> > Kraehbuehlstrasse 58, P.O. Box 514, CH-8044 Zurich, Switzerland
> >
> > Tel. +41 44 256 93 59
> > Fax +41 44 256 92 78
> > oliver.fuhrer@meteoswiss.ch
> > www.meteoswiss.ch - First-hand information
> >
> > _______________________________________________
> > ncl-talk mailing list
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>
>
Received on Thu Apr 29 10:26:01 2010