why is my vector bigger than how I created

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Khang Nguyen on 21 Nov 2020
Commented: Stephen Cobeldick on 22 Nov 2020
I tried to do a remain sum using matlab and graph it,
why is my sumvec vector is 101? should the while loop runs from 10 to 100
%equ = sqrt(x+1)
% calculating remain sum of sqrt(x+1) from with 10 to 100 sub interval
sum = 0
sumvec = []
for n = 10:100
sum = 0
width = (3 - 0)/n
for c = 0:n
base = width * c
height = sqrt(base+1)
sum = sum + (width * height)
end
sumvec(n+1) = sum
end
figure;
i = 0:101
scatter(i,sumvec)

1 Comment

Stephen Cobeldick on 22 Nov 2020
"why is my sumvec vector is 101? should the while loop runs from 10 to 100"
When n==100, which element do you expect this indexing to refer to?:
sumvec(n+1) = ..
Important: do NOT call any variable sum, as this shadows the very important inbuilt sum function.

Edited: Bastian Arturo Romero Mardones on 22 Nov 2020
Because the values are saved from space 11 onwards.
You must change n+1 in sumvec()
n+1 = 11 -- n-9 = 1
sum = 0
sumvec = []
for n = 10:100
sum = 0;
width = (3 - 0)/n;
for c = 0:n
base = width * c;
height = sqrt(base+1);
sum = sum + (width * height);
end
sumvec(n-9) = sum; %% change n+1 -- n-9
end
figure;
i = 1:length(sumvec) %i vector
scatter(i,sumvec)