Can experts have some words of wisdom to get me things please:

[tamoor]

function PowerAllo= waterfillingPowerAllo(Ptot,eigenVec)
eigenVec=eigenVec+1e-10;
eigenVec=eigenVec);
[sortedEigVec,oriPosition]=sort(eigenVec);

EigVecTemp=sortedEigVec;

begin=1;
while sum((EigVecTemp-EigVecTemp(1)*ones(length(EigVecTemp),1))./(EigVecTemp*EigVecTemp(1)))>Ptot
EigVecTemp=EigVecTemp(2:length(EigVecTemp));
begin=begin+1;
end

P1=(Ptot-sum((EigVecTemp-EigVecTemp(1)*ones(length(EigVecTemp),1))./(EigVecTemp*EigVecTemp(1))))/length(EigVecTemp);
for i=1:begin-1
PowerAlloOrdered(i)=0;
end

PowerAlloOrdered(begin)=P1;

for i=2:length(EigVecTemp)
PowerAlloOrdered(begin+i-1)=P1+(EigVecTemp(i)-EigVecTemp(1))/(EigVecTemp(i)*EigVecTemp(1));
end

for i=1:length(eigenVec)
PowerAllo(oriPosition(i))=PowerAlloOrdered(i);
end

sumCapa=0;
for i=1:length(eigenVec)
sumCapa=sumCapa+log2(1+PowerAllo(i)*eigenVec(i));
end

mu=P1+1/EigVecTemp(1);
capacity=sum(log2(mu*EigVecTemp));

, i got this from a website: i need to know how to use function: can any one make some example code and post please.
cheers :