Write a user-defined function that calculates the \"double factorial\" of a posi

Question

Write a user-defined function that calculates the "double factorial" of a positive odd integer (2n - 1)!! = (2n - 1)(2n - 3)(2n - 5)... (3)(1). For the function name and arguments, use y=dblfact (x) where the input argument x is the odd number whose double factorial is calculated and the output y is x!!. The function should display an error message if the input is not a positive integer. Use your function to evaluate the following:

(a) 7!! (b) 25!! (c) 12!! (d)(-13)!!

*Please read and follow the directions carefully.

Explanation / Answer

function y = dblfact (x)

if x<=0

disp('Error. Input is not a positive integer');

else

p=1;

for k=0:2:x-1

p=p*(x-k);

end

end

y=p;

>> dblfact(7)

ans =

105

>> dblfact(25)

ans =

7.9059e+12

>> dblfact(12)

ans =

46080

>> dblfact(-13)

Error. Input is not a positive integer

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