@rlopez 

Hello,

Thank you for all your suggestions.

I am still thinking on that one.

Best wishes

Bengu

Thank you very much for your interest 

Bengu 

@tomleslie 

Thank you very much for your interest in my problem.

Hovewer my worry is about the last equation in which the 

independent variable x is not seen. 

Are the constants A =2.9968... , and  B = -0.9272... correct result?

Thanks again

Bengu

@Thomas Richard 

Hello,

Thank you very much for your interest in my problem.

I am sure there is no typos my equation ( y= A*y^3+B*x  ;

where A and B are constants, x is independent variable and y is

dependent variable). 

Thanks again

Bengu

Dear Axel,

Thanks a lot

Best wishes

Bengu

Dear Axel,

This is

sin(theta)= a*sin(2*theta)-b*sin(4*theta)

which is in math terms and H is magnetic field. theta=0..Pi/2.  How did you guess that answer?

thank you

This is what I want to do. But I don't know how I put seq or $ command for a constrained polynomial fit. I think the number of elements could be equal.Thank you.

Best wishes

This is what I want to do. But I don't know how I put seq or $ command for a constrained polynomial fit. I think the number of elements could be equal.Thank you.

Best wishes

Y=-60,-50,.......+50,60

X= -1,-0.9,....+0.9,+1

Is that enough?

Y=-60,-50,.......+50,60

X= -1,-0.9,....+0.9,+1

Is that enough?