Maybe some previous result are interfering with your code, try this
clear
t=[0 .3 .5 .75 .95 .99];
for i = 1:length(t)
A = [0.0 0.0 .42;.6 0.0 0.0;0.0 0.75 t(i)];
[v,lambda] = eig(A);
lambdavector = max(lambda);
for y = 1:numel(lambdavector)
if max(abs(lambda(:))) == abs(lambdavector(y))
loc = y;
deig = lambda(y,y);
end
end
normv(:,i) = v(:,loc)/sum(v(:,loc));
end
c = normv(1,:);
y = normv(2,:);
a = normv(3,:);
figure
plot(t,abs(c),'b.-',t,abs(y),'g.-',t,abs(a),'r.-')
xlabel('Adult Survival Rate')
ylabel('Equilibrium Population')
title('Adult Survival Changed')
legend('Calves','Yearlings','Adults')
Some of your data are complex numbers, I replaced them by their modulus
You can also replace max(max(A)) by max(A(:))
