Getting the summation of a series

Hi,

I am trying to get the sum from the given equation below.

My h values and h and ah variables are shown

h=[ 1 3 5 7 9 11 13 15]

ah = [35.8577 -6.2962 -1.2855 3.9251 -3.8197 2.2690 -0.4077 -0.9397 ]

alpha = linspace(0, 2* pi, 15)

N(alpha) =

I have written the code below, however when I plot the summation vs alpha I do not get the correct shape of the graph.

Can you please help me with getting the summation and plotting it against the alpha ?

The graph supposed to look like below

Thank you

[Dyuman Joshi]

Note that the formulae in the image specifies that h is 1,2,3,4,....13,14,15 and not 1,3,5,...13,15.

And which sum do you want to plot? Regular sum (which will be a single value) or cummulative sum? Or any other sum? If so, then please define the sum.

[kalana agampodi]

Hi,

the values of h has to be the values of h that is in the vector.

For an example when,

n=1, h=1

n=2, h=3

n=3, h=5

And it is same for the ah values

n=1, ah = 35.8577

n=2, ah = -6.2962

I have attach the photo of the equation.

Answer 1

[Torsten]

h=[ 1 3 5 7 9 11 13  15] ;
ah = [35.8577   -6.2962   -1.2855    3.9251   -3.8197    2.2690   -0.4077   -0.9397 ];
alpha = linspace(0,2*pi,15).';
N = sum(ah.*cos(h.*alpha),2);
plot(alpha,N)

[kalana agampodi]

Thank you. I was thinking if I run through every element in the array using a for loop it will do the same thing. But apperently its matrix muliplication.

Thnaks

[Torsten]

@kalana agampodi

The indices for alpha and the (h,ah)-pairs must be different in your code. You used i for both of them.

Here is a code with a usual nested for-loop:

h=[ 1 3 5 7 9 11 13  15] ;
ah = [35.8577   -6.2962   -1.2855    3.9251   -3.8197    2.2690   -0.4077   -0.9397 ];
alpha = linspace(0,2*pi,15);
N = zeros(size(alpha));
for j = 1:length(alpha)
    for i=1:length(h)
        N(j) = N(j) + ah(i)*cos(h(i)*alpha(j));
    end
end
plot(alpha,N)