By default, when you plot() a single point, no marker is used. Also, no line is drawn unless you plot at least two points at the same time. Furthermore, you have not used "hold on" so your later plots erase the first.
You should use a different strategy:
dvals = 0 : 0.01 : 0.99;
for k = 1 : length(dvals)
d = dvals(k);
y(k)=1/(1+0.018*(d/(1-d)+d));
end
plot(dvals, y)
Or, more simply,
d = 0 : 0.01 : 0.99;
y = 1 ./ (1 + 0.018 .* (d ./ (1-d) + d));
plot(dvals, y)
