Trying to make a function for summing up 3 numbers. Explaination below

Konstantinos Kamperos

Konstantinos Kamperos (view profile)

님이 질문을 제출함. 29 Mar 2015
최근 활동 Stephen Cobeldick

Stephen Cobeldick (view profile)

님이 편집함. 30 Mar 2015
Youssef Khmou

Youssef Khmou (view profile)

님이 답변을 채택함.
Hello, I am trying to make a function that can split any type of number ( I am using Getdigits for that ) and sum the digits. I want the user to be able to input any digit number in a type of [x y z] and then be able to find if any of the numbers are odd. Unfortunately I am new to Matlab and I am not really able to make it work. Can anyone help me please. Thank you

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Answer by Youssef Khmou

Youssef Khmou (view profile)

on 29 Mar 2015

the following answer is an alternative approach without using 'getdigits' function :
function [C,y]=sum3(x)
h=int2str(x);
N=length(h);
for n=1:N
C(n)=str2num(h(n));
end
y=sum(C);

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Konstantinos Kamperos

Konstantinos Kamperos (view profile)

on 29 Mar 2015
Thank you a lot. This makes things way easier :). Is there any way to make this work for 3 numbers in a format of [x y z] without typing the code 3 times?

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Answer by Stephen Cobeldick

Stephen Cobeldick (view profile)

on 29 Mar 2015
Edited by Stephen Cobeldick

Stephen Cobeldick (view profile)

on 30 Mar 2015

Although an answer has already been accepted, that answer shows very poor use of MATLAB by solving this using nested loops and multiple calls to the rather slow str2num within each loop iteration. A much simpler, neater and faster solution would be to vectorize the whole code and use basic MATLAB practices, something like this:
>> A = [123,4,567890];
>> B = int2str(A(:))-48;
>> B(B<0) = 0
B =
0 0 0 1 2 3
0 0 0 0 0 4
5 6 7 8 9 0
>> sum(B,2)
ans =
6
4
35
This will work for vectors of any length (i.e. A can have any number of values in it), it will be faster that a loop-based solution (especially if A has more values in it), and it uses fewer lines of code too!

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Konstantinos Kamperos

Konstantinos Kamperos (view profile)

on 29 Mar 2015
Thank you a lot. It seems amazing. I do not yet understand how this code can work that well and be so small but I will research it. I appreciate your answer :)
Stephen Cobeldick

Stephen Cobeldick (view profile)

on 30 Mar 2015
MATLAB is a high-level language, which means that it has faster and neater ways of solving basic arithmetic than using loops: loops are the second choice in MATLAB, code vectorization is the preferred choice! Loops are what are needed in low-level languages like C, etc.
The concept is very simple: many basic arithmetic operations and MATLAB functions operate on complete matrices at once, without requiring any loops. This is called vectorization, and it is much faster, neater code, and it looks more like the mathematics as it would be written.
If you want to learn MATLAB, then do not learn bad programming habits first: instead learn the recommended practices and your code will be much improved.

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Answer by Youssef Khmou

Youssef Khmou (view profile)

on 30 Mar 2015
Edited by Youssef Khmou

Youssef Khmou (view profile)

on 30 Mar 2015

This function works for a vector of length n, with second logical output according to the description :
function [Logical,y]=sumn(x)
N=length(x);
for iter=1:N
h=int2str(x(iter));
NN=length(h);
C=zeros(1,NN);
for n=1:NN
C(n)=str2num(h(n));
end
S=sum(C);
y(iter)=S;
if mod(S,2)==0
Logical(iter)=true;
else
Logical(iter)=false;
end
end

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