MATLAB: Summation with for loops

loopssummation

Hi, I'm trying to plot the summation graph of y=1/(1+x)^2, so far my code is
x=[-10:10]
y=zeros(size(x))
for n=1:21
for k=1:11
terms= k.*(-x(n)).^(k-1)
y=y+terms
end
end
at the moment it is plotting a straight line but my friend believes this code is correct, any help is greatly appreciated.

Best Answer

I’m not certain what a ‘summation graph’ is.
One of these will probably do what you want: 
x = -10:10;
y = zeros(size(x));
for n=1:21
    for k=1:11
        terms(n,k) =  k.*(-x(n)).^(k-1);
    end
end
row_cumsum = cumsum(terms);
col_cumsum = cumsum(terms,2);
row_sum = sum(terms);
col_sum = sum(terms,2);
figure
plot(row_cumsum)
figure
plot(col_cumsum)
figure
plot(row_sum)
figure
plot(col_sum)
Experiment to get the result you want.
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