How to plot sum of series?

I am trying to plot the function above on interval [-2,2]. I was wondering if the code below is a correct way to do it.

 syms n x
    f(x)=symsum((((((-1)^(n+1))/(5*n)))*cos((n-1)*x)),n,1,Inf);
    figure
    fplot(x,[-2 2])

Also, how do I plot the partial sums F1,F2 and F10 on the interval [-2,2] and have them all on the same plot figure.

Answer 1

[Shubham Khatri]

Hello Teb,

Please take a look at the following code. You can change the value of n.

x=-2:.1:2
plot(x,expr(x))

function [value]=rbs(n,x)
value=(((((-1).^(n+1))/(5.*n))).*cos((n-1).*x));
end

function [ret]=expr(x)
ret=0;
for n=1:10
ret=ret+rbs(n,x)
end
end

Hope it helps

[Stefan]

Hi @Shubham Khatri

This is awesome, very nifty little piece of code, but powerful. Thank you so much

It took me a ton of research to come down to this and make it fit my project

I am working on my university assigment and this is what i got

% prep the workspace
clc
all clear
all clos
% variables 
x=0:.1:2;
y=expr(x);
% ploting results
plot(x,expr(x),'-o','MarkerIndices',1:2:length(y))
hold on
plot(x,log(x))
% bells and whistles
grid on
legend('Approximation (Taylor series)', 'ln(1)', 'Location', 'northwest')
title('Taylor Series Approximation of ln(1)')
xlabel('x')
ylabel('y')
% plugging in pre-calculated function
function [value]=rbs(n,x)
value=((-1).^(n+1)*(x-1).^n./n);
end
% summation of 5 degree of approximation
function [ret]=expr(x)
ret=0;
for n=1:5
    ret=ret+rbs(n,x);
end
end
% this is the end

[Walter Roberson]

@Stefan

Looks like it works, even if it is not as general as we might hope.

syms x
taylor(log(x), x, 1)

ans = 

expr(x)

ans = 

function [value]=rbs(n,x)
value=((-1).^(n+1)*(x-1).^n./n);
end
% summation of 5 degree of approximation
function [ret]=expr(x)
ret=0;
for n=1:5
    ret=ret+rbs(n,x);
end
end