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Problem 10 projecteuler.net matlab Summation of primes - solution

Problem

The sum of the primes below 10 is 2 + 3 + 5 + 7 = 17.
Find the sum of all the primes below two million. Solve using Matlab.

Solution

In this program we have used the for loop, if statement, isprime function, logical function, num2str function which are in built in matlab. Please head on to the below links if you don't know any of them:
Find the explanation of this program below

Program

sum = 0;
for i = 1:2000000
    if isprime(i) == logical(1)
        sum = sum+i;
    end
end
num2str(sum)

Download this program from here: sum_of_primes.m

Explanation

During the start of this program we have initiated the variable sum equal to 0. Now a for loop is started in the range of 1 to 2000000(2 million). Let us understand this problem by going through iterations.

First iteration

In the first iteration, the value of i is 1. Now the if statement starts and checks for the condition whether 1 is prime using the isprime function and the condition is false, So the statement inside the if statement (Add the value of the sum to the prime number, if the if statement is true) is not executed and the second iteration starts.

Second iteration

Now in the second iteration the value of the i is changed from 1 to 2. Condition for the if statement is satisfied and the statement inside the if statement gets executed. Now the value of the sum is changed from 0 to 0+2. Now again the third iteration starts

Third iteration

In the third iteration, the value of i is changed to 3 and the condition for the if statement is satisfied and the value of sum changed from 2 to 5. Similarly this continues till the value of the i is 2000000(2 million).

Finally num2str function is used to give the output of the sum of all the prime numbers below 2000000(2 million).

You may have a doubt on why I have converted the number to string using num2str instead of directly stating the output as number. I have tried this and I have found that the output is in the form of scientific notation(Ex. 1.408e+34), and this is not accurate, but as we need the accurate result, I have converted it to string and the output is accurate.

I have tried to explain this program so that even novice can understand it, but if you have doubt please don't hesitate to ask me the doubt you have.

You can download this post in pdf format and read it offline here: problem10_projecteuler_matlab.pdf

The code was highlighted using hilite.me

The problem has been taken from projecteuler.net and can be found here: problem10

Run the program and comment below the output you are getting for a given input.

 Keywords: problem 10, projecteuler.net, sum of primes, matlab
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