Adding uneven matrices

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B T
B T 2012-3-6
评论： Walter Roberson 2018-2-14
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!
  2 个评论
Andrei Bobrov
Andrei Bobrov 2012-3-6
please get the your example
Walter Roberson
Walter Roberson 2012-3-6
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.

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回答（2 个）

Jan
Jan 2012-3-6
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
  2 个评论
Ismail Qeshta
Ismail Qeshta 2018-2-14
Hi Jan. Can you please let me know how to modify your code for three unequal matrices instead of two? Thank you.
Walter Roberson
Walter Roberson 2018-2-14
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

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Andrei Bobrov
Andrei Bobrov 2012-3-6
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
>>

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