[ncl-talk] regCoef_n without y-axis intercept

Dennis Shea shea at ucar.edu
Thu Oct 27 11:30:57 MDT 2022 

Oops. I inadvertently did not attach the fortran codes.



On Thu, Oct 27, 2022 at 11:09 AM Dennis Shea <shea at ucar.edu> wrote:

> This thread is a bit hard to follow for me.
>
> [1] re: "Now I'm thinking how to make the function to force the regression
> to pass from origin. Any idea on how to do that?"
>      I do not know how to accommodate the additional constraint of making
> the regression line'go through the origin.
>      Likely, googling something like "regression line through the origin"
> will yield some information.
>
> [2] Make sure your modified fortran subroutine works. Initially, code and
> test this only for one-dimension. We can do multiple dimensions later.
>     EG with the 'gfortran' compiler.
>      I took NCL's underlying fortran subroutine. I changed the source name
> to RCGRAF/rcgraf to avoid any possible naming conflicts. I wrote a simple
> fortran driver. Any  fortran compiler will work
>
>      %> gfortran tst_regcoef.f regcoef_graffino.f        <=== compile
> fortran codes
>       %> ./a.out
> <=== execute the compiled codes
>
>        rcoef=  0.974561453
>         tval =   38.7428589
>         yint =   15.3522949
>
> [3] Now, modify the "regcoef_graffino.f  " to create a regression line
> where there is no y-intercept
>
> [4] Repeat step [2] with your modified code.
>
> [5] Create a .so file via
>
>      %> WRAPIT regcoef_graffino.f
>
>       will create regcoef_graffino.so
>
> [6] Create a simple 1D test of invoking the .so file and print results
>
> [7] At this point, we can make a 2nd subroutine that invokes the .so file
> multiple times.
>
>
>
>
>
>
>
>
>
>
>
> If The (hidden) C interface to the f77 subroutine just loops over the
> appropriate dimensions and returns the various results.
>
> ---
> If you have 1D arrays [ X[N], Y[N] ]
>
>
> On Wed, Oct 26, 2022 at 9:10 AM Dave Allured - NOAA Affiliate via ncl-talk
> <ncl-talk at mailman.ucar.edu> wrote:
>
>> Giorgio, WRAPIT is capable of handling arrays correctly.  I suggest you
>> try some of the working fortran examples in the WRAPIT documentation, so
>> that you can get familiar with WRAPIT and array arguments.  Then, get the
>> *original* regcoef_dp.f working with WRAPIT and arrays, but change the
>> function name to prevent conflict.  It might be helpful to write external
>> standalone fortran main programs that call the fortran routines you are
>> testing, to ensure those routines are working independently from NCL.
>>
>> Only after that, try interfacing your modified routine with WRAPIT.
>> Please completely avoid regcoefW.c.  It is full of internal protocol that
>> is not related to WRAPIT and will continue to confuse you.
>>
>> I do not have time to analyze or debug your code and procedures.  If
>> needed, perhaps someone else is available.
>>
>>
>> On Wed, Oct 26, 2022 at 3:09 AM Giorgio Graffino <g.graffino at tim.it>
>> wrote:
>>
>>> Hi Dave,
>>>
>>> Thanks for confirming that. I'm changing the fortran subroutine Dennis
>>> sent last week into a function, but it keeps giving me an error wherever I
>>> try to use arrays as arguments. It only works when X and Y are scalar
>>> numbers. I really don't understand how a linear regression fit can be found
>>> with scalar numbers as arguments. I'm looking at the C interface to see how
>>> to subroutine is called, but there are too many things happening in
>>> regcoefW.c and it's difficult to understand the workflow. Can anyone please
>>> help me understand how to make the fortran subroutine work for 1d and 2d
>>> arrays?
>>>
>>> Cheers,
>>>
>>> Giorgio
>>>
>>>
>>> ------ Messaggio Originale ------
>>> Da: dave.allured at noaa.gov
>>> A: g.graffino at tim.it
>>> Cc: ncl-talk at ucar.edu
>>> Inviato: lunedì 24 ottobre 2022 22:10
>>> Oggetto: Re: [ncl-talk] regCoef_n without y-axis intercept
>>>
>>> Giorgio, you are right, regcoefW.c is an NCL internal interface routine
>>> for regCoef_n. But it uses a different protocol than a WRAPIT interfaced
>>> function. Just ignore regcoefW.c, and follow the WRAPIT fortran
>>> instructions carefully, for your new function. Change the function name,
>>> and do not attempt to replace the built-in regCoef_n function. You can
>>> change the arguments as you like, but follow the documented WRAPIT rules.
>>>
>>> There are two different methods for calling external C functions:
>>> fortran wrapper, and shared object. Please study the WRAPIT documentation
>>> carefully.
>>>
>>>
>>> On Mon, Oct 24, 2022 at 1:35 PM Giorgio Graffino via ncl-talk <
>>> ncl-talk at mailman.ucar.edu> wrote:
>>>
>>>> Hello,
>>>>
>>>> I'm doing some modifications to the regcoef_dp.f file to consider a
>>>> zero y-intercept, but now I don't know how to try it in a script. The
>>>> number of arguments in the fortran subroutine is different than in
>>>> regCoef_n, so the subroutine is probably going through some more steps,
>>>> possibly involving this script (
>>>> https://github.com/NCAR/ncl/blob/develop/ni/src/lib/nfp/regcoefW.c).
>>>> Am I right?
>>>>
>>>> How can I incorporate both fortran and C scripts in my NCL script? I
>>>> know I can use WRAPIT to read external fortran code, but what about C code?
>>>>
>>>> I need help please.
>>>>
>>>> Giorgio
>>>>
>>>>
>>>> ------ Messaggio Originale ------
>>>> Da: ncl-talk at mailman.ucar.edu
>>>> A: shea at ucar.edu
>>>> Cc: ncl-talk at ucar.edu
>>>> Inviato: venerdì 21 ottobre 2022 13:14
>>>> Oggetto: Re: [ncl-talk] regCoef_n without y-axis intercept
>>>>
>>>> Hi Dennis, Dave
>>>>
>>>> Thanks for sending the relevant function and for explaining how to
>>>> access the source code. Now I'm thinking how to make the function to force
>>>> the regression to pass from origin. Any idea on how to do that?
>>>>
>>>> Cheers,
>>>>
>>>> Giorgio
>>>>
>>>>
>>>> ------ Messaggio Originale ------
>>>> Da: shea at ucar.edu
>>>> A: g.graffino at tim.it
>>>> Cc: dave.allured at noaa.gov; ncl-talk at ucar.edu
>>>> Inviato: giovedì 20 ottobre 2022 19:17
>>>> Oggetto: Re: [ncl-talk] regCoef_n without y-axis intercept
>>>>
>>>> The f77 code is attached.
>>>>
>>>>
>>>> On Thu, Oct 20, 2022 at 9:53 AM Giorgio Graffino via ncl-talk <
>>>> ncl-talk at mailman.ucar.edu> wrote:
>>>>
>>>>> Hi Dave,
>>>>>
>>>>> Thanks for the advice. I looked at the examples in
>>>>> https://www.ncl.ucar.edu/Applications/regress.shtml, especially
>>>>> examples 2 and 4, but I couldn't find any supplementary information about
>>>>> regCoef. I also can't find anything under
>>>>> $NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl and
>>>>> $NCARG_ROOT/lib/ncarg/nclscripts/csm/contributed.ncl.
>>>>>
>>>>> Is NCL source code located anywhere in $NCARG_ROOT? Can anyone please
>>>>> point me where it is?
>>>>>
>>>>> Cheers,
>>>>>
>>>>> Giorgio
>>>>>
>>>>>
>>>>> ------ Messaggio Originale ------
>>>>> Da: dave.allured at noaa.gov
>>>>> A: g.graffino at tim.it
>>>>> Cc: ncl-talk at ucar.edu
>>>>> Inviato: giovedì 13 ottobre 2022 18:47
>>>>> Oggetto: Re: [ncl-talk] regCoef_n without y-axis intercept
>>>>>
>>>>> Giorgio, for your second question, please see this very brief
>>>>> description that I recently wrote, for how to search for functions in the
>>>>> NCL source code.
>>>>> https://mailman.ucar.edu/pipermail/ncl-talk/2022-August/018954.html
>>>>>
>>>>>
>>>>> On Thu, Oct 13, 2022 at 10:38 AM Giorgio Graffino via ncl-talk <
>>>>> ncl-talk at mailman.ucar.edu> wrote:
>>>>>
>>>>>> Hi NCL community,
>>>>>>
>>>>>> I want regCoef_n to find the regression coefficient between two
>>>>>> arrays without y-axis intercept. Do you know how I can change the function
>>>>>> to do that?
>>>>>>
>>>>>> Can you also please tell me where I can find the function? I did a
>>>>>> grep recursive search in my $NCARG_ROOT directory but I couldn't
>>>>>> find it.
>>>>>>
>>>>>> Cheers,
>>>>>>
>>>>>> Giorgio
>>>>>>
>>>>> _______________________________________________
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>
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