Trying to make symsum work.

I am having problems getting symsum to calculate the following sumation within this equation:

I am using the following code to get pi:

function piram
  %approximates and prints pi with Ramanujan's formula
  %called as piram or piram()
  %doesn't return a value, but a print
  
  k=sym('k');
  sumpart=symsum((factorial(4*k)*(1103+26390*k))/(((factorial(k))^4)*(396^(4*k))),k,0,inf);
  inverted=sumpart*((2*sqrt(2))/9801);
  approxpi=1/inverted;
  fprintf('Using Ramanujan''s formula, a good approximation is %.6f\n',approxpi)
end

Can anyone help with this?

[Jacob Oleshchuk]

Sidenote: My error occurs within the symsum

Answer 1

[Steven Lord]

If the only factorial function that appears when you execute:

which -all factorial

is the one included in MATLAB, you probably don't have Symbolic Math Toolbox installed. Check the output of the ver function to test whether you have it installed. If you don't have Symbolic Math Toolbox installed, I would have expected the sym or syms calls to error before you even reached the line where you called symsum, but it's possible you've written your own functions named sym or syms that are being used instead of the versions from Symbolic Math Toolbox.

If what you posted in response to madhan ravi's question was the output of which factorial (without the -all flag) try it with the -all flag and show us what that returns.

[Walter Roberson]

People who have the MATLAB Connector for Maple installed but not the Symbolic Toolbox would have access to sym and syms but would be missing access to several symbolic functions.

[Steven Lord]

Good to know.

[Jacob Oleshchuk]

I have tried to install the Symbolic Toolbox to no avail as the 'unzipper' (for lack of better term) has an error at the very end of execution. However, I believe that if this works for everyone else who DOES have that program extension, I should just be able to include a note with my project that informs my teacher that they require the Symbolic Toolbox to run the final function of my program (piram). Thanks much.

[Walter Roberson]

As you are a student you might be able to test your code on MATLAB Online .

Answer 2

[madhan ravi]

function piram
syms k
sumpart=symsum((factorial(4*k)*(1103+26390*k))/(((factorial(k))^4)*(396^(4*k))),k,0,inf);
  inverted=sumpart*((2*sqrt(2))/9801);
  approxpi=1/inverted;
  fprintf('Using Ramanujan''s formula, a good approximation is %.6f\n',approxpi)
end

[Jacob Oleshchuk]

is...is my only issue with how i have the symbolic k set?

[Jacob Oleshchuk]

Wait, no this didn't fix the code, now it's saying this:

Error using factorial (line 20)

N must be an array of real non-negative integers.

Error in piram (line 7)

sumpart=symsum((factorial(4*k)*(1103+26390*k))/(((factorial(k))^4)*(396^(4*k))),k,0,inf);

[madhan ravi]

clear all at the very beginning of the code , I got the answer in terms of pi as a decimal value , see attached picture

[Jacob Oleshchuk]

function piram
  %approximates and prints pi with Ramanujan's formula
  %called as piram or piram()
  %doesn't return a value, but a print
  clear all
  syms k
  sumpart=symsum((factorial(4*k)*(1103+26390*k))/(((factorial(k))^4)*(396^(4*k))),k,0,inf);
  inverted=sumpart*((2*sqrt(2))/9801);
  approxpi=1/inverted;
  fprintf('Using Ramanujan''s formula, a good approximation is %.6f\n',approxpi)
end

This is my new code, it still results in:

Error using factorial (line 20)
N must be an array of real non-negative integers.

Error in piram (line 7)
  sumpart=symsum((factorial(4*k)*(1103+26390*k))/(((factorial(k))^4)*(396^(4*k))),k,0,inf);
  
Error in ProgramPi (line 34)
      piram

[Jacob Oleshchuk]

I have what you have in your picture my guy, are you sure you didn't fix something subconciously?

[madhan ravi]

I didn‘t have any trouble getting the result after running your code , ok type whos k in command window and paste the result here. or try

syms k positive

leaving the rest of the code unchanged

[Jacob Oleshchuk]

>> whos k
>> piram
Error using factorial (line 20)
N must be an array of real non-negative integers.

Error in piram (line 7)
  sumpart=symsum((factorial(4*k)*(1103+26390*k))/(((factorial(k))^4)*(396^(4*k))),k,0,inf); 
>> whos k
>> 

i get nothing

[madhan ravi]

I have no clue what mistake you did

[Jacob Oleshchuk]

i'm 99% sure the mistake is in my factorial somewhere

[Jacob Oleshchuk]

Seeing as that it keeps telling me,

Error using factorial (line 20)

N must be an array of real non-negative integers.

[madhan ravi]

whos factorial

which -all factorial

in command window what does it show?

[Jacob Oleshchuk]

C:\Program Files\Matlab\R2018a\toolbox\matlab\specfun\factorial.m

[madhan ravi]

Did you try

syms k positive  %?

[Walter Roberson]

What shows up for

which factorial(k)

Question: is it possible that you have Maple installed but not the MATLAB Symbolic Toolbox ?

[madhan ravi]

@Jacob please respond to sir Walters question