Try this:
x = [0.001 0.01 0.1 1 10];
y = [63.5 74.5 94.1 94.2 103.5];
fcn = @(b,x) b(1).*x.^b(2);
B0 = rand(2,1);
B = lsqcurvefit(fcn, B0, x, y)
figure
plot(x, y, 'p')
hold on
plot(x, fcn(B,x), '-r')
hold off
set(gca, 'XScale','log') % Optional
grid
xlabel('X')
ylabel('Y')
legend('Data', sprintf('y = %.3f\\cdotx^{%.3f}', B), 'Location','E')
.
