Adding uneven matrices

Hey guys,

is there a method(aka function) by which I can add two matrices that aren't the same size and make it so that the matrices become of equivalent size by being filled with zeros in the remaining space?

Thanks

[Merged information from Answer]

It would be like ..

a=ones(150,91)*2

b=ones(141,100)*3

a+b

So, is there a way to make the matrices even but filling them with zeros? (adding 0 more rows to b, and 9 more columns to a of value=0) ...

Thanks!

[Andrei Bobrov]

please get the your example

[Walter Roberson]

There are over 100,000 different possible results for that calculation. You need to be very specific about which elements are to be added to which elements.

Answer 1

[Jan]

a = ones(150,91)*2
b = ones(141,100)*3
c = AddFill(a, b);

function c = AddFill(a, b);
sa = size(a);
sb = size(b);
c = zeros(max(sa, sb));   % Pre-allocate
c(1:sa(1), 1:sa(2)) = a;  % Assign a
c(1:sb(1), 1:sb(2)) = c(1:sb(1), 1:sb(2)) + b;  % Add b

[Ismail Qeshta]

Hi Jan. Can you please let me know how to modify your code for three unequal matrices instead of two? Thank you.

[Walter Roberson]

function d = AddFill(a, b, c);
sa = size(a);
sb = size(b);
sc = size(c);
d = zeros(max([sa; sb; sc]));   % Pre-allocate
d(1:sa(1), 1:sa(2)) = a;  % Assign a
d(1:sb(1), 1:sb(2)) = d(1:sb(1), 1:sb(2)) + b;  % Add b
d(1:sc(1), 1:sc(2)) = d(1:sc(1), 1:sc(2)) + c;  % Add c

Answer 2

[Andrei Bobrov]

variant (one of 100000) :)

function out = addiffmatrix(varargin)
n = cellfun('ndims',varargin);
N = max(n);
sz = cell2mat(cellfun(@(x)[size(x) ones(1,N - numel(size(x)))],varargin(:),'un',0));
mm = arrayfun(@(i1)1:i1,sz,'un',0);
m1 = zeros(max(sz));
out = m1;
M = m1;
for j1 = 1:numel(varargin)
  M(mm{j1,:}) = varargin{j1};
  out = out + M;
  M = m1;
end

using

a = ones(3,4)
b = 2*ones(5,3)
out = addiffmatrix(a,b)
out =
     3     3     3     1
     3     3     3     1
     3     3     3     1
     2     2     2     0
     2     2     2     0

ADD

variant with "general point"

function out = addiffmatrix(cp,varargin)
% cp - coordinates of the  general point in every matrix
% varargin - matrices

n = cellfun('ndims',varargin);
N = max(n);
sz = cell2mat(cellfun(@(x)[size(x) ones(1,N - numel(size(x)))],...
                                                           varargin(:),'un',0));
C = max(cp);
ij1 = bsxfun(@minus,C,cp);
mm = arrayfun(@(i1,j1)(1:i1)+j1,sz,ij1,'un',0);
out = zeros(C+max(sz-cp));
for j1 = 1:numel(varargin)
    out(mm{j1,:}) = out(mm{j1,:}) + varargin{j1};
end

using

>> a
a =
     1     1     1     1
     1     1     1     1
>> b
b =
          1.5          1.5          1.5
          1.5          1.5          1.5
          1.5          1.5          1.5
>> c
c =
     2     2
     2     2
     2     2
     2     2
     2     2
>> cp
cp =
     1     1
     1     3
     5     2
>> out = addiffmatrix(cp,a,b,c)
out =
            0            2            2            0            0            0
            0            2            2            0            0            0
            0            2            2            0            0            0
            0            2            2            0            0            0
          1.5          3.5          4.5            1            1            1
          1.5          1.5          2.5            1            1            1
          1.5          1.5          1.5            0            0            0
>>