# MATLAB for Loop Examples

A MATLAB for loop is a repetition control structure that allows you to efficiently write a loop that needs to
execute a specific number of times.

The MATLAB for loop syntax is given as

```for index = values
<program statements>
...
end```

## MATLAB for loop Examples

1. Write a program to display numbers from 1 to 5.

```for p = 1:1:5
disp(p)
end```

Result 2. Write a program to display values which are decrementing by 0.8 at each step. The series start at 9 and end at 6.

```for p = 9:-0.8:6
disp(p)
end```

Result 3. Write a program to display the following pattern. ```p=input('enter row number = ')%enter row number to generate pattern upto that row
x = [];
for i = 1 : p
x = strcat(x,'*');
disp(x)
end```

Result 4. Write a program to display the following pattern. ```p=input('enter row number = ')%enter row number to generate pattern upto that row
x = [];
for i = 1 : p
x = strcat(x,'*');
s = [blanks(p-i) x];
disp(s)
end```

Result 5. Write a program to display the following pattern. ```n=input('enter row number = ')%enter row number to generate pattern upto that row
for i=n+1:-1:2
for j=i-1:-1:1
fprintf('*');
end
fprintf('\n');
end```

Result 6. Write a program to sum all 1, 2, and 3 digit prime numbers

Method-1

```total = 0;
for k = 1:999
if(isprime(k))
total = total + k;
end
end
disp(total)```

Method-2

```total = 0;
for k = primes(999)
total = total + k;
end
disp(total)```

Result

76127

7. Write a program to duplicating each element of a vector. For example, given the vector [1 4 3], we want to end up with [1 1 4 4 3 3].

Method-1

```V = 1:5; % sample vector
for j = 1:length(V)
V2((2*j-1):(2*j)) = V(j);
end
disp(V2)```

Method-2

```V = 1:5; % sample vector
for j = 1:(2*length(V))
V2(j) = V(ceil(j/2));
end
disp(V2)```

Method-3

```V = 1:5; % sample vector
counter = 0.5;
for j = 1:(2*length(V))
V2(j) = V(ceil(counter));
counter = counter + 0.5;
end
disp(V2)```

Result 8. Write a program that finds all 4 digit twin primes (numbers separated by two that are both primes)

```for x = 1001:2:9997
if(isprime(x) & isprime(x+2))
fprintf('%0f and %0f are both prime\n',x,x+2)
end
end```

Result .

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