Summation loop (sigma notation) help
6 views (last 30 days)
Show older comments
Please help! I am slowly but surely understanding Matlab, but struggle a bit every now and then. I am trying to make a summation loop out of:
a=1:100; n=2; sum_a=0.5; for ii=1:length(a); sum_a=sum_a + a(ii).^n; end display(sum_a);
The way i read it is that (a)^n + (a+a)^n + (a+a+a)^n....
Is this correct?
Many thanks :D
0 Comments
Answers (3)
Mischa Kim
on 10 Feb 2014
In your code
sum_a = 0.5;
for ii = 1:length(a)
sum_a = sum_a + a(ii).^n;
end
you initially set sum_a = 0.5. In the loop you then add a(ii).^n to the previously stored value of sum_a. In other words:
ii = 1: sum_a = 0.5 + 1^2 ... which equals 1.5
ii = 2: sum_a = 1.5 + 2^2 ... which equals 5.5
ii = 3: sum_a = 5.5 + 3^2 ... which equals 14.5
...
Iain
on 10 Feb 2014
If you want: (a)^n + (a+a)^n + (a+a+a)^n....
What you actually want is:
a = 0.5; % or whatever
sum = 0;
n = 2;
for i = 1:m % m being the limit
sum = sum + (i*a)^n
end
So, if m is 0, you get sum = 0, if m is 1, you get 0.25, if m is 2, sum = 1.25, m = 3, sum = 3.5, m = 4 sum = 7.5 ...
See Also
Categories
Find more on Loops and Conditional Statements in Help Center and File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!