why will my function not take my array 'slope' as an answer. I am writing code to differentiate an equation by finding the average gradient.

error messages

function ret4=numerical_df(self)
            x=[0.00000 0.000002 0.000004 0.000006 0.000008 0.000010]
            y=[0 0 0 0 0 0 ]
            slope=[0 0 0 0 0 0 ]
            for n=1:6
                y(n)=(self.a*x(n)*x(n)*x(n))+(self.b*x(n)*x(n))+(self.c*(n))+self.d;
            end
            for n=1:6
                dx=x(n+1)-x(n);
                dy=y(n+1)-y(n);
                slope(n)=dy/dx;
            end
                ret4=slope
              
           % ?????????
            
        % for next question do differnce between df values 
        end
    

Error using my_maths_class/numerical_df

Too many input arguments.

Index exceeds the number of array elements (6).

Error in my_maths_class/numerical_df (line 74)

dx=x(n+1)-x(n);

[Torsten]

y(n)=(self.a*x(n)*x(n)*x(n))+(self.b*x(n)*x(n))+(self.c*x(n))+self.d;

instead of

y(n)=(self.a*x(n)*x(n)*x(n))+(self.b*x(n)*x(n))+(self.c*(n))+self.d;

[Tom Kirkland]

thank you

Answer 1

[Jan]

If n==6, you request x(7) in:

dx = x(n+1)-x(n);

There is no x(7). y(n+1) must fail also. The error message is clear.

There are only 5 steps between 6 elements.

[Tom Kirkland]

thank you that has solved it