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 Taking derivatives of functions in Origin C		  New Topic  Reply to Topic
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gpoon

USA
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Posted - 07/21/2009 :  2:31:06 PM  Show Profile  Edit Topic  Reply with Quote  View user's IP address  Delete Topic
Origin Ver. 8 and Service Release (Select Help-->About Origin): SR4
Operating System: XP

I am trying to take numerical derivatives of functions (not a dataset of points) in Origin C. I noticed that the NAG library doesn't have a function for differentiation for C (but does for Fortran). The GNU Scientific Library (GSL) does have such a function, but I cannot get it to work because, apparently, Origin C doesn't support calling external functions that return a struct type variable.

So this is what I was trying in my "ocgsl.h" file:

/* Definition of an arbitrary function with parameters */

struct gsl_function_struct
{
double (* function) (double x, void * params);
void * params;
};

typedef struct gsl_function_struct gsl_function ;

GSL_EXPORT int gsl_diff_central (const gsl_function *f,
double x,
double *result, double *abserr);

Does Origin C (or NAG) have a differentiation function (for functions) that I just don't know about? Is there any way to overcome this limitation of calling functions that return struct type variables? Many thanks!

Iris_Bai

China
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Posted - 07/21/2009 :  11:39:55 PM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
Hi,

Could you give more details about not work, for example compiling error?
Origin C doesn't support external functions that return a struct type variable, but support struct type as output variable. In your code above, gsl_function is a struct and in gsl_diff_central function it is a output variable, not a return value. So should work in Origin C.

Any way, you can reference to:
http://wiki.originlab.com/~originla/internal/index.php?title=Tutorial:Fitting_with_Integral_Function_using_GSL_routine

http://ocwiki.originlab.com/index.php?title=OriginC:Calling_GNU_Scientific_Library



Iris
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gpoon

USA
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Posted - 07/22/2009 :  6:04:23 PM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
Hi Iris!

Thanks for your reply. When I tried to compile "ocgsl.h" as follows (using the example on OriginWiki was a template):

#pragma dll(libgsl, header)
// this is OC special pragma,
// header keyword is to indicate libgsl.dll is in same location as this file

#define GSL_EXPORT // for OC, this is not needed, so make it empty

// you can directly search and copy gsl function prototypes here

struct gsl_function_struct
{
double (* function) (double x, void * params); <---
void * params;
};

typedef struct gsl_function_struct gsl_function ;

GSL_EXPORT int gsl_diff_central (const gsl_function *f,
double x,
double *result, double *abserr);

The compiler returns "Error, syntax error in function declaration" at the line marked with the arrow. What is my mistake?

Thanks,
Gregory
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Iris_Bai

China
Posts
Posted - 07/22/2009 :  11:36:09 PM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
Hi Gregory,

Please try the following way to define a function pointer outside strcut:

typedef double (* FUNC)(double x, void * params);

struct gsl_function_struct
{
	FUNC function;
	void * params;
};


Iris
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gpoon

USA
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Posted - 07/27/2009 :  02:16:46 AM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
It works! Thanks!
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