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 Fitting a plot using a user defined function		  New Topic  Reply to Topic
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nesrin9002

USA
2 Posts
Posted - 04/15/2014 :  9:51:14 PM  Show Profile  Edit Topic  Reply with Quote  View user's IP address  Delete Topic
Hi,
Can someone help me with this;
I am trying to write user defined function to fit my plot.

The equation I have to fit is z=Sum{z_n * Sin(n*x)}
summation is over n, from lets say 0 to N.
x(angles) is the values on the x axis in my plot.

Thanks,
Nesrin.

nesrin9002

USA
2 Posts
Posted - 04/16/2014 :  1:22:44 PM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
So far I have this:

void _nlsfsum(
// Fit Parameter(s):
double y0,
// Independent Variable(s):
double x,
// Dependent Variable(s):
double& y)
{
// Beginning of editable part
double c[11];
double d[11];
for(int i=1; i<=10; i++)
{

y=y0+c[2*i+1]* sin((2*i+1)*x) + d[2*i]* cos(2*i*x);



}

It compiles but doesn't work when I fit it to the data.
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greg

USA
1378 Posts
Posted - 05/01/2014 :  09:07:17 AM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
I am not sure how your second post relates to the first.
In the second you declared two arrays of double (c & d) which you did not initialize (so they are all zero).
Even if you fixed that, your use of each array ( c[2*i+1] and d[2*i] ) over the range i = 1 to 10 would produce indices which were out of bounds of the arrays.
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long nguyen

Vietnam
1 Posts
Posted - 05/23/2014 :  9:23:04 PM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
it difficult to understand .
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MaggotsBrain

Japan
4 Posts
Posted - 05/25/2014 :  10:14:43 PM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
maybe this can help you: http://www.originlab.de/www/helponline/Origin/en/mergedProjects/Tutorial/Tutorial/User_Defined_Fitting_Function_using_OC.html
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