This is easier to do with plot than with scatter:
x = 1:5;
y = [2 3 NaN; 5 2 4; 3 NaN NaN; 6 5 3; 1 3 4]; % Matrix With Multiple ‘y’ Values For Each ‘x’
figure(1)
plot(x, y, 'pg')
grid
axis([0 6 0 10])
EDIT —
If you absolutely must use scatter, this works:
x = [1 1 2 2 2 3 4 4 4 5 5 5];
y = [2 3 5 2 4 3 6 5 3 1 3 4];
figure(1)
scatter(x, y, 'pg')
grid
axis([0 6 0 10])
The plot option is easier.