how to vectorize these "for loop" ?
1 Ansicht (letzte 30 Tage)
Ältere Kommentare anzeigen
clc;
clear all;
close all;
i=1;
for k=1:1:10;
for a=1:1:10;
for b= 1:1:10;
for c=1:1:10;
nump(i,:)=[k a*k];
denmp(i,:)=[1 b+c b*c];
i=i+1;
end
end
end
end
1 Kommentar
Christos Saragiotis
am 4 Aug. 2017
If the only reason you want to vectorize is speed and k, b have the same range (i.e. from 1 to 10) and likewise a, c have the same range you can take advantage of this and make this quadruple for-loop a double one.
The following implementation is about 40 times faster than the posted one on my machine:
N = 10; % nb, nk
M = 10; % na, nc
NM = N*M;
Num = zeros(NM,2);
Den = zeros(NM,3);
k = 1;
for n = 1:N;
for m = 1:M;
Num(k,:) = [n n*m];
Den(k,:) = [1 n+m n*m];
k = k+1;
end
end
Denmp = repmat(Den,NM,1);
Num = reshape(Num, 1,NM,2);
Nump = repmat (Num, NM,1,1);
Nump = reshape(Nump, NM*NM,2);
Akzeptierte Antwort
fbaillon
am 4 Aug. 2017
If you want to vectorize your problem, you can write something like this:
n=10;
m=n*n;
%
A=repmat(1:n,n*m,1);
B=repmat(1:n,m,n) ;
C=repmat((1:n),n*m,1);
nump=[A(:) B(:).*C(:)];
%
B=repmat(1:n,n,1)+repmat((1:n)',1,n);
C=repmat(1:n,n,1).*repmat((1:n)',1,n);
denmp=[ones(m*m,1) repmat(B(:),m,1) repmat(C(:),m,1)];
Maybe we can make it even faster...
Fabien Baillon.
1 Kommentar
Jan
am 4 Aug. 2017
Since Matlab 2016b you can replace e.g.
C = repmat(1:n,n,1).*repmat((1:n)',1,n);
by
C = (1:n) .* (1:n)';
In older versions:
C = bsxfun(@times, 1:n, (1:n).');
Weitere Antworten (2)
Andrei Bobrov
am 4 Aug. 2017
Bearbeitet: Andrei Bobrov
am 4 Aug. 2017
[c,b,a,k] = ndgrid(1:10);
nump = [k(:), a(:).*k(:)];
denmp = [ones(numel(k),1), b(:)+c(:), b(:).*c(:)];
1 Kommentar
KL
am 4 Aug. 2017
Bearbeitet: KL
am 4 Aug. 2017
c = 1:10;
c1 = reshape(repmat(c,1000,1),[10000,1]);
c2 = reshape(repmat(c,100,10),[10000,1]);
nump1 = [c1, c1.*c2];
dc2 = repmat(cell2mat(arrayfun(@(a,b) a:b, 2:11,11:20, 'UniformOutput', false)),1,100)';
dc3 = repmat(cell2mat(arrayfun(@(a,b,s) a:s:b, c,10:10:100,c, 'UniformOutput', false)),1,100)';
denmp1 = [ones(10000,1), dc2, dc3];
isequal(nump,nump1)
isequal(denmp,denmp1)
0 Kommentare
Siehe auch
Kategorien
Mehr zu External Language Interfaces finden Sie in Help Center und File Exchange
Produkte
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!