Hi everyone. I'm working on a piece of code and I'm having a bit of trouble with array pre-allocation. Here it is:(adsbygoogle = window.adsbygoogle || []).push({});

function [react_in1 react_in2 react_out1 react_out2]=oneVtwoXone(masses,prec);

prec = 1e-4;

N=length(masses);

masses=[0;masses]; % adding dummy metabolite with zero mass

masses=masses(:);

%mass2=masses*ones(size(masses))'+ones(size(masses))*masses';

%mass2=mass2(:);

mass2=zeros(N*(N+1)/2,1); % list of mass pairs

met1=mass2; % list of the first metabolite in a pair

met2=mass2; % same for the second metabolite

k=0;

for i=1:N

for j=i:N

k=k+1;

met1(k)=i;

met2(k)=j;

mass2(k)=masses(i)+masses(j);

end

end

disp(['Number of distinct pairs is' length(mass2) ])

[mass2, ord]=sort(mass2); % sorted mass pairs

met1=met1(ord); % metabolites in the same order as sorted mass pairs

met2=met2(ord);

dm=diff(mass2);

while(length(find(dm <= mass2(1:length(dm))*prec)) > 0) % while have metabolite pairs that have about the same mass

ind=find(dm<mass2(length(mass2)-length(dm)+1:end)*prec);

react_in1=[react_in1 met1(ind)];

react_in2=[react_in2 met2(ind)];

react_out1=[react_out1 met1(ind+1)];

react_out2=[react_out2 met2(ind+1)];

dm = dm(1:end-1) + dm(2:end);

end

disp(['Number of conforming reactions is' length(react_in1) ])

The source of my trouble is in the second while loop. The react_in1 etc. takes up too much memory and I need to figure out how to preallocate a matrix to hold values approximately 10000, and how to delete the excess zeros if there is any unused space.

Can anyone help?

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# MATLAB Array Pre-allocation help!

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