| T O P I C R E V I E W |
| deanwilk |
Posted - 10/18/2004 : 12:20:28 AM
Origin Version (Select Help-->About Origin): 7.5
Operating System: Windows 2000
I am trying to fit data to a cumulative normal distribution (or cumulative lognormal distribution). I don't see the cumulative distribution listed in the funtions. Is there a simple way to add this distribution to the functions Origin is capable of fitting?
My next challenge is to take the difference between the cumulative distribution for two neighboring values, e.g., cumnormaldist(x,mean,sigma)-cumnormaldist(x-1,mean,sigma). I then want to fit this difference of the normal distribution to some data I have on hand. Can you suggest a simple way to program the difference of the cumulative distribution into Origin so I can use this as the fitting function?
Thanks for your help! |
| 3 L A T E S T R E P L I E S (Newest First) |
| Mike Buess |
Posted - 12/18/2006 : 07:04:48 AM
Add this below #include <Origin.h> at the top of _nlfuser2.fit...
double norm_cdf(double x, double mu = 0, double sigma = 1);
Mike Buess
Origin WebRing Member
Edited by - Mike Buess on 12/18/2006 07:15:10 AM |
| mruehrig |
Posted - 12/17/2006 : 8:08:03 PM
quote:
Hi,
The cumulative normal distribution function is available in the NAG library under the function named nag_cumul_normal(x). You can call this function from your custom fitting function in NLSF. Note that to call the NAG function in your NLSF fitting function, you should first edit your fitting function in code builder (click the Edit in Code Builder button in the NLSF tool), and then replace all the #include statements at the top of the function with just one statement:
#include <origin.h>
Now, the nag_cumul_normal() function assumes a mu (centroid) of zero and sigma (std dev) of 1. So if you want something more general, I suggest that you define a new Origin C function as follows:
1> Go to code builder and start a new C file - give it a name say for example MyFunctions.c
2> Add the following function to that file and compile
double norm_cdf(double x, double mu = 0, double sigma = 1)
{
if( sigma > 0 )
return nag_cumul_normal( ( x - mu ) / sigma );
else
return NANUM;
}
3> Now your new function norm_cdf() will allow computing the cumulative distribution for a specified mu and sigma
4> In Code Builder, drag-and-drop the file from the User folder to the System folder. Then this function will be available any time you launch Origin
5> Then, in NLSF, you can refer to this function in your custom fitting function code using the syntax
norm_cdf(x, mu, sigma). Note that mu and sigma default to 0 and 1 respectively if not specified.
Easwar
OriginLab
Tried this but it does not work. I generated the folowin plot of a log normal distribution and tried to fit it wit a user defined function "user2"
y = norm_cdf(x, mu, sigma),
but fittig does not start, even.
When compiling in the Code builder of NLSF I get the following error messages:
C:\Programme\OriginLab\OriginPro75\Manni\OriginC\NLSF\_nlfuser2.fit(37) :Error, function or variable norm_cdf not found
C:\Programme\OriginLab\OriginPro75\Manni\OriginC\NLSF\_nlfuser2.fit(37) :Error, general compile error
C:\Programme\OriginLab\OriginPro75\Manni\OriginC\NLSF\_nlfuser2.fit(28) :Error, error(s) found in compiling function _nlsfuser2
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| easwar |
Posted - 10/18/2004 : 4:33:54 PM
Hi,
The cumulative normal distribution function is available in the NAG library under the function named nag_cumul_normal(x). You can call this function from your custom fitting function in NLSF. Note that to call the NAG function in your NLSF fitting function, you should first edit your fitting function in code builder (click the Edit in Code Builder button in the NLSF tool), and then replace all the #include statements at the top of the function with just one statement:
#include <origin.h>
Now, the nag_cumul_normal() function assumes a mu (centroid) of zero and sigma (std dev) of 1. So if you want something more general, I suggest that you define a new Origin C function as follows:
1> Go to code builder and start a new C file - give it a name say for example MyFunctions.c
2> Add the following function to that file and compile
double norm_cdf(double x, double mu = 0, double sigma = 1)
{
if( sigma > 0 )
return nag_cumul_normal( ( x - mu ) / sigma );
else
return NANUM;
}
3> Now your new function norm_cdf() will allow computing the cumulative distribution for a specified mu and sigma
4> In Code Builder, drag-and-drop the file from the User folder to the System folder. Then this function will be available any time you launch Origin
5> Then, in NLSF, you can refer to this function in your custom fitting function code using the syntax
norm_cdf(x, mu, sigma). Note that mu and sigma default to 0 and 1 respectively if not specified.
Easwar
OriginLab
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