How to calculate arithmetic series?

Hi, I am new to mathlab. I want to evaluate an array and don't know how to do it with mathlab. Here are the two of the examples: n Sigmma notation i = i=1

n Signma notation i^2= i=1

Note: sigma notation means sums

Thanks. Susi

[Jan]

@Susi: The program is called "Matlab". To be exact, the manufacturer prefers MATLAB.

If your mean "sum", I think the term "sum" is better than "sigma notation". It is not clear what "n Sigma notation i=i=1" means. Can you explain this again?

[Grzegorz Knor]

@Susi,look at symsum:

http://www.mathworks.com/help/toolbox/symbolic/symsum.html

Answer 1

[David Young]

Does your first example look like this:

      n
     SUM i
     i=1

and your second example look like this:

      n   
     SUM i^2
     i=1

where I'm using SUM to stand for a capital sigma symbol?

If so, you would evaluate them in MATLAB like this:

n = 100; % set n to whatever value you need
i_vector = 1:n;     
s1 = sum(i_vector);
s2 = sum(i_vector.^2);

To understand these examples, it's essential to look up the colon ( : ) operator in the introductory documentation or your textbook, as it's at the core of how this kind of operation is usually done. Also look at the documentation for the sum function, and for the .^ operator.

[Jan]

The elements of arithmetic series have a constant difference. Therefore (i_vector.^2) is not an arithmetic series.

"sum(1:n)" and "sum((1:n).^2" can be calculated without creating "1:n" explicitely, which is much cheaper for large n.

Answer 2

[Susi D]

Hi Guys, Thanks for your input=)You have been a great help. Yes, David, those are what I meant: n SUM i i=1

and

n SUM i^2 i=1

And Jan, hmmm....ya....I just remembered that arithmetic series shouldn't have ^2 =)

Best Regards =) Susi D

Answer 3

[Susi D]

Opps sorry, I don't know why my typing became a mess when it was posted.

So, yes, I meant:

 n
 SUM i
 i=1

and

 n
 SUM i^2
 i=1