Try this:
x = linspace(0, 1000, 20);
y = exp(0.01*x);
figure
plot(x, y)
grid
title('Original')
figure
plot(x, y)
grid
xt = get(gca, 'XTick');
set(gca, 'XTickLabel', fliplr(xt))
title('Flipped X')
The first figure is the original data, the second is the same, with the x-tick values reversed.
