Problem with factorial recursive function
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Whenever I run the code for a matrix of n values, like n=1:10, only the last 2 factorials are displayed while the rest are 0's. Would anyone be able to tell me where I have gone wrong?
Code:
function x = fact(n)
if n<=1
x = 1;
else
x = n .* fact(n-1) ;
end
end
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Risposte (5)
Titus Edelhofer
il 28 Gen 2015
Hi Arun,
your code does not work for arrays because of the "if n<=1". You would need to do something like
idx = (n>1);
x(~idx) = 1;
x(idx) = n(idx).* ...
Titus
3 Commenti
John D'Errico
il 28 Gen 2015
For how large of a value are you trying to compute the factorial? Be careful, as this could be important, since that too would blow up the recursion limits.
Regardless, as you have written it, the code will still run forever. What happens when all values of n are <= 1?
The function as you wrote it will still call fact, but with an empty array for n. so you will have fact calling fact, each time with an empty argument n.
I would add a test to stop that from happening.
Shubham Tyagi
il 15 Ago 2016
I'm compiling this code with a 2*4 matrix but (dimensions doesn't match in val(i)=r(i).*fact(r(i)-1);) type error is coming.
function val=fact(r)
i=(r>1); val(~i)=1; if r==1 return end val(i)=r(i).*fact(r(i)-1); end
Image Analyst
il 31 Gen 2015
Not sure what you did, but it worked fine for me. I put all this (both functions) into test.m
function test
clc;
for k = 1 : 10
kFactorial = fact(k);
fprintf('%d! = %d\n', k, kFactorial);
end
function x = fact(n)
if n<=1
x = 1;
else
x = n .* fact(n-1) ;
end
In the command window you'll see:
1! = 1
2! = 2
3! = 6
4! = 24
5! = 120
6! = 720
7! = 5040
8! = 40320
9! = 362880
10! = 3628800
4 Commenti
Image Analyst
il 15 Ago 2016
I don't know what matrix you're talking about. Please give the code you are going to run to call your function, and show what output you'd expect to see.
If you want fact n to print out an array from the first integer to the last integer, the fact() function will need to be modified since now it's just expecting a single number, not a vector or matrix.
Torsten
il 25 Ago 2016
Reshape everything to vectors and reshape back to matrices, if necessary.
Best wishes
Torsten.
Titus Edelhofer
il 25 Ago 2016
Hi,
two minor changes are needed:
function x = fact(n)
x = ones(size(n));
idx = (n>1);
if any(idx)
x(idx) = n(idx).*fact(n(idx)-1);
end
First, you need to initialize x as an array of the same size as n (because for fact(n-1) otherwise the array could be smaller), giving the error you observed.
Second, protect the recursive call to fact(n-1) by doing this only if there is anything to do...
Titus
1 Commento
Titus Edelhofer
il 26 Ago 2016
Calling for a matrix works fine, btw.:
fact([2 3 4; 5 6 7])
ans =
2 6 24
120 720 5040
Anil Sarode
il 26 Dic 2017
Modificato: Walter Roberson
il 26 Dic 2017
sorry i copied your code :
this is the one way to solve your problem :
function file: from where you make function call each time using for loop :
n=1:10;
y=[];
for i=1:length(n)
y(i)=fact(i) ;
end
function: which do desire task
function [x] = fact(n)
if n<=1
x = 1;
else
x = n .* fact(n-1) ;
end
end
0 Commenti
Abdimalik
il 14 Dic 2022
You don't need to read input or print anything. Your task is to complete the function factorial() which takes an integer N as input parameters and returns an integer, the factorial of N.
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