# Вопрос по matlab – Как найти ближайший вектор к данному вектору в Matlab?

0

У меня есть набор n-мерных представительных векторов в Matlab. Я должен сгруппировать векторы из набора обучающих векторов в группы, представленные репрезентативными векторами на основе близости. Как я должен это делать?

Ваш Ответ

2   ответа
1

``````function mcd = MCD(fiber1, fiber2, option)

%

%remove NaNs
fiber1(find(isnan(fiber1),1):length(fiber1),:) = [];
fiber2(find(isnan(fiber2),1):length(fiber2),:) = [];

dist = 0;

for k = 1:length(fiber1)

D = [];

for j = 1:length(fiber2)
D = [D distance(fiber1(k,:),fiber2(j,:))];
end;

dist = dist + min(D);

end;

mcd = dist / length(fiber1);

if nargin > 2

dist = 0;

for k = 1:length(fiber2)

D = [];

for j = 1:length(fiber1)
D = [D distance(fiber2(k,:),fiber1(j,:))];
end;

dist = dist + min(D);

end;

mcd2 = dist / length(fiber2);

if strcmp(option,'mean')
mcd = mean([mcd mcd2]);
elseif strcmp(option,'min')
mcd = min([mcd mcd2]);
end;
end;
``````

``````function mcd = MCD(fiber1, fiber2, option, sampling)

%MCD(fiber1, fiber2)
%MCD(fiber1, fiber2, option)
%MCD(fiber1, fiber2, option, sampling)

%remove NaNs
fiber1(find(isnan(fiber1),1):length(fiber1),:) = [];
fiber2(find(isnan(fiber2),1):length(fiber2),:) = [];

%sample the fibers for speed. Each fiber is represented by "sampling"
%number of points.

if nargin == 4

freq = round(length(fiber1)/sampling);
fiber1 = fiber1(1:freq:length(fiber1),:);
freq = round(length(fiber2)/sampling);
fiber2 = fiber2(1:freq:length(fiber2),:);

end;

%reshape to optimize the use of distance() for speed
FIBER2 = reshape(fiber2',[1,3,length(fiber2)]);
FIBER1 = reshape(fiber1',[1,3,length(fiber1)]); %this is only used in the symmetrical case, i.e when 'min' or 'mean' option is called

%reshape amd tile filber 1 so as to eliminate the need for two nested for
%loops thus greatly increasing the computational efficiency. The goal is to
%have a 4D matrix with 1 row and 3 columns. Dimension 3 is a smearing of
%these columns to be as long as fiber2 so that each vector (1x3) in fiber1
%can be placed "on top" as in a row above the whole of fiber2. Thus dim 3
%is as long as fiber2 and dim 4 is as long as fiber1.

fiber1 = reshape(fiber1',[1,3,length(fiber1)]); %1x3xF1
fiber1 = repmat(fiber1,[length(FIBER2),1,1]); %F2x3xF1
fiber1 = permute(fiber1,[2,1,3]); %3xF2xF1
fiber1 = reshape(fiber1,[1,3,length(FIBER2),length(FIBER1)]);%1,3,F2,F1

mcd = mean(min(distance(fiber1, repmat(FIBER2,[1,1,1,length(FIBER1)]))));

if nargin > 2

fiber2 = reshape(fiber2',[1,3,length(fiber2)]); %1x3xF1
fiber2 = repmat(fiber2,[length(FIBER1),1,1]); %F2x3xF1
fiber2 = permute(fiber2,[2,1,3]); %3xF2xF1
fiber2 = reshape(fiber2,[1,3,length(FIBER1),length(FIBER2)]);%1,3,F2,F1

mcd2 = mean(min(distance(fiber2, repmat(FIBER1,[1,1,1,length(FIBER2)]))));

if strcmp(option,'mean')
mcd = mean([mcd mcd2]);
elseif strcmp(option,'min')
mcd = min([mcd mcd2]);
end;
end;
``````

``````function Edist = distance(vector1,vector2)

%distance(vector1,vector2)
%
%provides the Euclidean distance between two input vectors. Vector1 and
%vector2 must be row vectors of the same length. The number of elements in
%each vector is the dimnesionality thereof.

Edist = sqrt(sum((diff([vector1;vector2])).^2));
``````