Re: [ferret_users] how to do embedded expression inside an embedded expression with grave accent

[Karl Smith - NOAA Affiliate <karl.smith@xxxxxxxx>]

Hi Xiaoyu,

Similar to Billy's comment, in the repeat loop, define a symbol with the file number, then issue the "use" command using that symbol.  So something like:

    let filenames = spawn("/bin/ls -1 /path/to/files/*.nc")

    repeat /I=1:37 ( define symbol filenum = `I`; use `filenames[I=($filenum)]` )

If you are trying to do more complicated things in the repeat loop, consider writing a script that gets called each time.

In this case the script (calling it usefilenamesnum.jnl for this example) is very trivial, but would look something like:

    ! usefilenamesnum.jnl

    ! Usage:  usefilenamesnum  filenames  filenum

    ! where:

    !    filenames = string array variable containing file names

    !    filenum = number of the filename to use

    use `($1)[I=($2)]`

 

And then the repeat loop would look like:

   repeat /I=1:37 go usefilenamesnum filenames `I`

Both of there methods break up two back-tic evaluations.

Karl

On Wed, Oct 10, 2018 at 10:40 AM Xiaoyu Bai <xbai1@xxxxxxxx> wrote:

Hi Billy,

Thank you for the suggestion 😸. However, I have 37 files. Read them in clusters might be easier for me.

Have a good day.

Xiaoyu

On Wed, Oct 10, 2018 at 1:15 PM William Kessler <william.s.kessler@xxxxxxxx> wrote:

I'm not sure I understand your question exactly, but I think a defined symbol has highest priority. Ferret will simply drop that symbol into any command. And note that symbols can be embedded (see example).

If you only have 7 of these then the symbols can be defined manually:

def sym root "/home/xbai1/Tracmip/family1/"
def sym f1 "whatever_your_first_filename_is.nc"
def sym f2 "whatever_your_second_filename_is.nc"
...
def sym f7 "whatever_your_last_filename_is.nc"

repeat/range=1:7:1/name=fnum (let dummy=`fnum`; def sym sfnum `dummy`; use "($root)($f($sfnum))"; ... )

I'm not sure why, but this kind of syntax inside a repeat loop requires defining a new dummy variable to use for symbol definition.

Billy


> On Oct 10, 2018, at 9:36 AM, Xiaoyu Bai <xbai1@xxxxxxxx> wrote:
>
> repeat/range=1:7/name=aa (use file_name_`aa`.nc) is a good idea. I have a handicap that I use let files_CNRM=spawn("ls -1 /home/xbai1/Tracmip/family1/*CNRM*.nc") to identify my files before I read them in. Ferret doesn't let me to use syntax `spawn("ls -1 /home/xbai1/Tracmip/family1/*CNRM*.nc")` because grave accent has the highest priority. 😹
>
> Thanks a lot.
> Xiaoyu
>
> On Wed, Oct 10, 2018 at 11:52 AM Satyesh Ghetiya <satyeshghetiya@xxxxxxxxx> wrote:
> Hi,
>
>
> On Wed, Oct 10, 2018 at 9:05 PM Xiaoyu Bai <xbai1@xxxxxxxx> wrote:
> Hi Ghetiya,
>
> Yes, I wan to read all the files in through the repeat loop. When you say nested loop, do you mean let datset=0; repeat/range=1:8 (let datset=`datset+1`; use `files_CNRM[X=datset]`)? It didn't work.
>
> ^ Yes, you are correct, I also encountered similar problem, it seems ferret is not taking nested definition of variable.
> The error message is like **ERROR: command syntax: DATSET // SET DAT/FORM=CDF `files_CNRM[X=datset]`. I feel datset needs a pair of grave accent to make it as an variable. However, ferret considers the nearest two grave accents as a pair.
> I might need to read my files in one by one instead of using repeat loop.
>
> ^ But once I used syntax like this which worked: repeat/range=1:7/name=aa (use file_name_`aa`.nc;)
> Anyway if not, then yes for now, you may have to use one by one.
> Thank you very much and have a nice day.
>
> Welcome.
>
> On Wed, Oct 10, 2018 at 12:53 AM Satyesh Ghetiya <satyeshghetiya@xxxxxxxxx> wrote:s
> Hi,
> I also faced similar problem, but every time I am by passing using two grave accent by using some other repeat loop (nested) or by using some other variable.
> Are you wanting to use, in loop, 7 data sets ? 
>
> On Wed, Oct 10, 2018 at 1:53 AM Xiaoyu Bai <xbai1@xxxxxxxx> wrote:
> Dear ferreters,
>
> I have a syntax that's like repeat/range=1:7/name=datset use `files_CNRM[x=`datset`]`. However, ferret reads it like  `files_CNRM[x=` and `]`. So I am wondering how to make this syntax work.
>
> Thank you very much.
> --
> Xiaoyu
>
>
> --
> G Satyesh
>
>
>
> --
> Xiaoyu
>
>
> --
> G Satyesh
>
>
>
> --
> Xiaoyu

--

Xiaoyu

--

Karl M. Smith, Ph.D.
JISAO Univ. Wash. and PMEL NOAA
"The contents of this message are mine personally and do
not necessarily reflect any position of the Government
or the National Oceanic and Atmospheric Administration."