It is not clear what you are asking for. Maybe one of these 2 idea help you:
1. Change the x values:
x = 1:10; % Some test data, use your original signal
y = rand(1, 10);
subplot(1,2,1);
plot(x, y);
subplot(1,2,2);
plot(x * 2, y); % Or what ever change you need in x
2. Interpolation:
xx = linspace(x(1), x(end), 2 * numel(x))
yy = interp1(x, y, xx)
plot(x, y, 'o');
hold on
plot(xx, yy, '+');
