"FOR" loop

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Juan Alvarez
Juan Alvarez on 4 Dec 2011
I have to find the prime numbers from that lead up to 100 and then use the 'for' function to multiply adjecent prime numbers: example:
first prime numbers
2 3 5 7
and i need the 'for' to do the following with the prime numbers
2*3 3*5 5*7 etc...HELP PLEASE
  1 Comment
Dinesh Kannan Natarajan
Dinesh Kannan Natarajan on 28 Apr 2021
% to Generate prime number between the intervals
clear;
clc;
m=input('provide the required start point of prime number: ');
n=input('provide the required end point of prime number: ');
if n<=0
pr='Error';
disp('ERROR: Input argument must be a positive integer')
elseif round(n)~=n||round(m)~=m
pr='Error';
disp('ERROR: Input argument must be positive integer')
elseif n <= m
pr='Error';
disp('ERROR: end point must be greater than start point')
else
k=1;
for i=m:n
c=0;
for j=2:i-1
if rem(i,j)==0
c=1;
break
end
end
if c==0
pr(k)=i;
k=k+1;
end
end
end
pr

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Answers (4)

Junaid
Junaid on 4 Dec 2011
let say your prime vector is P;
p=primes(100);
a = zeros(1,length(p)-1);
for i=1:length(p)-1
a(i) = p(i) * p(i+1);
end
a
though you can do it also without loop but you asked for a loop so it is loop solution.
  1 Comment
Juan Alvarez
Juan Alvarez on 4 Dec 2011
im sorry but this did not help...
i am at here so far
k=primes(100)
then it list the primes but i cant figure out how to use the for loop at all

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Junaid
Junaid on 4 Dec 2011
p=primes(100);
A = zeros(1,length(p)-1);
for i=1:length(p)-1
A(i) = p(i) * p(i+1);
end
A
just copy and paste the code, answers is in vector (A) try this, do let us know if it is what you wanted to do.
  1 Comment
Juan Alvarez
Juan Alvarez on 6 Dec 2011
This helped a lot!! thanks!

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Sean de Wolski
Sean de Wolski on 6 Dec 2011
Loop sure seems like overkill
x = primes(100);
x1p1 = x(1:end-1).*x(2:end);

Andrei Bobrov
Andrei Bobrov on 4 Dec 2011
a = 1:100;
yourprime = a(a - sum(rem(triu(bsxfun(@rdivide,a,a.')),1)>0)<=2);
out = prod(yourprime(bsxfun(@plus,1:numel(yourprime)-1,(0:1)')))
  1 Comment
Paulo Silva
Paulo Silva on 6 Dec 2011
It takes a while for me to understand your code, nicely done

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