MATLAB: Two vectors different from each other at least at two points

different row vectorsMATLAB

I want to compare two vectors and check whether they are different at least at two coordinates.

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sum(abs(V1-V2)~=0)>=2

Will output 1 if they differ at two or more indices. You may want to set a tolerance if they are floating point numbers.

tol=0.01
sum(abs(V1-V2)>tol)>=2

Related Solutions

MATLAB: How to subtract specific elements in matrix

Assumption: There's always one and only one non-zero element in each matrix, and the matrices have the same size

assert(all(sum(ob ~= 0, 2) == 1) && all(sum(tb ~= 0, 2) == 1)) %check 1st assumption
assert(isequal(size(ob), size(tb))) %check 2nd assumption

Step 1: find the indices of non-zero column in each row using find. Because find works column-wise, transpose the matrices and the problem becomes: find non-zero row in each column:

[obcol, ~] = find(ob'); %the ~ is required as you want the two return value version of find
[tbcol, ~] = find(tb');

Step 2: compare the indices and when they differ extract the corresponding element from each matrix using sub2ind:

differcol = obcol ~= tbcol;
rowindices = (1:size(ob, 1))';
rowindices = rowindices(differcol); %indices of row where non-zero column differ
obvalues = ob(sub2ind(size(ob), rowindices, obcol(differcol)));
tbvalues = tb(sub2ind(size(tb), rowindices, tbcol(differcol)));

Step 3: subtract the differences and sum it all:

diffsum = sum(obvalues - tbvalues)

MATLAB: Finding three columns in one variable in another variable

I tried a simple vectorized solution of permute and sum of squares approach, but ran into "out of memory" issues:

>> C = dlmread('CoarseTjointMesh.txt','',9,0); %Fibre Orientation @ Elements. Read text file, first few lines not needed
>> C(:,2:4) = C(:,2:4)*1e-3; % Convert mm into m
>> F = dlmread('matrix.txt','',0,0); %Fibre Orientation and Position data at elements
>> B = 3*8*size(C,1)*size(F,1)
B =  13703964384
>> num2sip(B) % Oops... I don't have 14 GBytes of memory
ans = 13.704 G

However using a cell array worked without error, and is just as simple:

% split into row vectors in cell array:
tmp = num2cell(C(:,2:4),2);
% find indices of closest set of points:
fun = @(v)min(sum((v-F(:,8:10)).^2,2)); % requires >=R2016b
[dst,idx] = cellfun(fun,tmp);
% get output rows selected by those indices:
out = F(idx,2:7);

Note that the subtraction inside the anonymous function requires scalar dimension expansion, which was introduced in R2016b. For earlier versions replace the subtraction with bsxfun.

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Related Solutions

MATLAB: How to subtract specific elements in matrix

MATLAB: Finding three columns in one variable in another variable

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