Adding two row arrays that are different lengths

I have to write a function to add two row arrays together for any large number as if you were adding them on a calculator. I can't get them to add if they aren't the same length as it says 'Matrix dimensions must agree'. I know you need to use the zeros function but I can't figure it out. e.g. i have to make [1,2,3,4,5] + [1,2,3] go to [1,2,3,4,5] +[0,0,1,2,3]

Also how to you make the remainder go onto the next number e.g.: [2,3,4,5] + [2,3,4,5] = 4 6 9 0 instead of 4 6 8 10??

Any help would be great!

Answer 1

[Sean de Wolski]

The first one:

x = [1 2 3 4 5]
y = [1 2 3]

z = x+padarray(y,[0, numel(x)-numel(y)],0,'pre')

The second:

x = 2:5
y = 2:5

z = mod(x+y,10)

Answer 2

[Star Strider]

This works:

First part:

a1 = [1 2 3 4 5];
a2 = [1 2 3];
a2ix = (1+length(a1)-length(a2)):length(a1);
a2(a2ix) = a2;
a2(1:a2ix(1)-1) = zeros(1,a2ix(1)-1);

Output for the first part: ‘a1’ and ‘a2’.

Second part:

b1 = [2 3 4 5];
b2 = [2 3 4 5];
c = 0;                                  % Initial Carry = 0
for k1 = length(b1):-1:1
    b3(k1) = b1(k1)+b2(k1)+c;           % Add + Carry
    c = fix(b3(k1)/10);                 % Generate Carry
    b3(k1) = b3(k1)-(c*10);             % Subtract 10*Carry
end

Output for the second part: ‘b3’.

Answer 3

[Kelly Kearney]

Wouldn't it be easier to just convert your arrays to single numbers and add?

 array2num = @(x) sum(10.^(length(x)-1:-1:0) .* x);
 num2array = @(x) str2num(num2str(x)')';

 x = [1 2 3 4 5];
 y = [1 2 3];
 num2array(array2num(x) + array2num(y))

 ans =

     1     2     4     6     8

 x = [2 3 4 5];
 y = [2 3 4 5];
 num2array(array2num(x) + array2num(y))

 ans =

     4     6     9     0

Answer 4

[Azmat Ameen]

function[t,x]=padding(t1,t2,x1,x2)
t=min(min(t1),min(t2)):max(max(t1),max(t2));
y1=zeros(1,length(t));
y2=y1;
y1((t>=min(t1))&(t<=max(t1)))=x1; 
y2((t>=min(t2))&(t<=max(t2)))=x2;
x=(y1+y2)
stem(t,x)
end               

Use this function to pad zeros and you will get the addition of two different array with different length.