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How to use meshgrid to replace the nested for loops

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Leo Tu
Leo Tu 2021년 7월 12일
답변: Leo Tu 2021년 7월 13일
I have the following script
load("Temperature.mat") % labelled T
T = T'; % from column vector to row vector
AT = T-min(T); % this is the adjusted positive temperatures
r = mypoiss(5,0.5,1,AT); % r is a 1x12504 double, for simpilicity let it contain the values 1:12504
s = 0:3; % lag range
om = 0.1:0.1:0.4; % decay rate range
mu = 0.1:0.1:0.4; % baseline rate range
Ns = numel(s);
Nom = numel(om);
Nmu = numel(mu);
nll = nan(Ns,Nom,Nmu);
for si = 1:Ns
for omi = 1:Nom
for mui = 1:Nmu
nll(si,omi,mui) = mylikelihood(s(si),om(omi),mu(mui),AT,r);
end
end
end
[ss,omm,muu]=meshgrid(s,om,mu);
scatter3(ss(:),omm(:),muu(:),[],nll(:))
and the following function
function nll = mylikelihood(s,om,mu,AT,r)
% output; nll is the negative log likelihood
% input; s is lag, om is decay rate, mu is baseline rate
% T is temperatures, t = time in days
t = max(s)+1:numel(AT);
nll = 0;
for ti = 1:numel(t)
k = abs(s:-1:(s-t(ti)+1));
id = ((t(ti)-1):-1:0)+1;
lambda = mu+sum(om.^k.*AT(id))/sum(om.^k);
% store all the results
nll = nll - (r(ti).*log(lambda)) + (lambda);
end
Is it possible to use meshgrid to replace the use of the two nested for loops (for omi and mui) so that I am left with just the following in the loop bit
for si = 1:Ns % here I want to just be looping for values of si
nll = % ... etc
end
If anyone can point me in the right direction for using meshgrid to do this that would be helpful, thank you.

채택된 답변

Leo Tu
Leo Tu 2021년 7월 13일
New script:
load("Temperature.mat")
T = T'; % from column vector to row vector
AT = T-min(T); % this is the adjusted positive temperatures
r = mypoiss(5,0.5,1,AT);
s = 0:3; % lag range
om = 0.1:0.1:0.4; % decay rate range
mu = 0.1:0.1:0.4; % baseline rate range
Ns = numel(s);
Nom = numel(om);
Nmu = numel(mu);
nll = nan(Ns,Nom,Nmu);
for si = 1:Ns
omi = 1:Nom;
mui = 1:Nmu;
nll(si,omi,mui) = mylikelihood2(s(si),om,mu,AT,r,Nom,Nmu);
end
[ss,omm,muu]=meshgrid(s,om,mu);
scatter3(ss(:),omm(:),muu(:),[],nll(:))
New function:
function nll = mylikelihood2(s,om,mu,AT,r,Nom,Nmu)
% output; nll is the negative log likelihood
% input; s is lag, om is decay rate, mu is baseline rate
% T is temperatures, t = time in days
t = max(s)+1:numel(AT);
[omm,muu] = meshgrid(om,mu);
nll = zeros(Nom,Nmu);
for ti = 1:numel(t)
k = abs(s:-1:(s-t(ti)+1));
id = ((t(ti)-1):-1:0)+1;
lambda = muu+sum(omm(:).^k.*AT(id))/sum(omm(:).^k);
% store all the results
nll = nll - (r(ti).*log(lambda)) + (lambda);
end

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