How do I store data to plot it from a summation?

I want to be able to store the data for each new term that is generated and plot it. with k/b to be the x axis and term results on the y axis. I am not sure how to do this.

[madhan ravi]

people can’t run images upload your code

[Sierra Bounds]

function cosx = mycos(a,b)
k = 0;
term = 0;
%term = zeros(1,121);
while k < b %IDK about infinity...
    k2 = 2*k;
    top = (((-1)^k) * (a^k2));
    bot = factorial(k2);
    term = term + (top / bot);
    k = k + 1;
end 
cosx = term;
end

Answer 1

[KSSV]

function cosx = mycos(a,b)
k = 0;
term = 0;
%term = zeros(1,121);
x = zeros([],1) ; 
y = zeros([],1) ;

while k < b %IDK about infinity...
    k2 = 2*k;
    top = (((-1)^k) * (a^k2));
    bot = factorial(k2);
    term = term + (top / bot);
    k = k + 1;
    x(k) = k/b ;
    y(k) =term ;
end 
cosx = term;
plot(x,y,'.r')
end

[Sierra Bounds]

Is there a way to do it with lines, instead of dots?

[KSSV]

plot(x,y,'r')