Stopping the output of a for cycle in matlab

Question

I'm facing an issue with this simple Fibonacci number generator program:

function f = fibonr(n)
f(1) = 1; 
f(2) = 1;
    for i = 3:n
    f(i) = f(i-1) + f(i-2);
    end

end

If I want to display only the n-th number of the sequence, what adjustments should I make?

Once the for-loop is completed (after n iterations) the nth number will be the last one stored in `f` right? You can then display `f(end)` after the `end` statement of the loop. Is it what you mean? — Benoit_11, Oct 05 '15 at 19:23
I did as you' ve said, but in this case I get two outputs: the first one with the last number stored, and the answer of the program with the whole vector of numbers — james42, Oct 05 '15 at 19:29

score 2 · Answer 1 · edited May 23 '17 at 12:22

2

function f = fibonr(n)
f = zeros(n,1); %//initialise the output array
f(1,1) = 1;
f(2,1) = 1;
for ii = 3:n
    f(ii,1) = f(ii-1,1) + f(ii-2,1);
end
%//create a string with text and variables
str = sprintf('The %d th number in the Fibonacci sequence is %d',n,f(ii,1));
disp(str) %//display your output.
end

first up: don't use i as a variable. Secondly, I switched to using column vectors, since MATLAB processes them faster, as well as I initialised the array, which is way faster (hence the shiny orange wiggles below your f(i)= line).

Call your function:

output = fibonr(10);
The 10 th number in the Fibonacci sequence is 55

If you use e.g. n=20 and still want the 10th argument just call output(10)

edited May 23 '17 at 12:22

Community

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answered Oct 05 '15 at 19:27

Adriaan

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May you explain me what the statement zeros(n,1) means? – james42 Oct 05 '15 at 19:31
This doesn't solve my problem. I have tried using your code, but what I get is an infinite list of the nth number – james42 Oct 05 '15 at 19:38
Just use the function as presented and the code below "call your function" in your command window. – Adriaan Oct 05 '15 at 19:39
Yes, but I want that the program gives me back immediately the output, without further interaction... Is this possible? – james42 Oct 05 '15 at 19:41
Also, don't write `for ii=3:inf`;) – Andras Deak -- Слава Україні Oct 05 '15 at 19:50
Sorry, probably I'm being obnoxious, but is there any way to suppress the output given by ans? I want the program to display only the nth number! – james42 Oct 05 '15 at 19:51
2

Yes, there is, use the semicolon like I showed you in the answer. Please *read* the answer carefully and *copy the code exactly* – Adriaan Oct 05 '15 at 19:51
But I've put the semicolon after f(ii)=f(ii-1,1) + f(ii-2,1); it just doesn't suppress the output! I don't know why it happens... I'm using matlab 2012 anyway – james42 Oct 05 '15 at 19:57
2

Because you are calling your function like `fibonr(10)` and not like I showed you in my answer. – Adriaan Oct 05 '15 at 19:59

score 0 · Answer 2 · answered Oct 05 '15 at 20:16

if you want the specified output right away you can use nargin. This code will give you all of the sequence if you call fibonr(n), or you can specify a vector to get the fibonacy numbers at said positions. If you are interested in both, your specified output and all the numbers, you can call the function with: [output, fibnumbers] = fibonr(n,v);

function [output,f] = fibonr(n,v)
f(1) = 1; 
f(2) = 1;
    for i = 3:n
    f(i) = f(i-1) + f(i-2);
    end

 if nargin() > 1
     output = f(v);
 else
     output = f;
end

Stopping the output of a for cycle in matlab

2 Answers2