method 1:

p := [`$`([n, 1], n = 2 and n = 3 and n = 5 and n = 7)]

plot(l, x = 0 .. 15, style = point, symbol = circle)

how to make method 1 right,I know if n=1..7,that's right,but n should be prime numbers.

Is there prime plot?

question2:

plot(piecewise(x = 2, 1), x = -2 .. 6) or plot(piecewise(x = 2 and x=3 and x=5 and x=7, 1), x = -2 .. 6)

why this is not right,I can't see the point (2,1)...(3,1),(5,1),(7,1)

question3:

add plot label directly,p1 := plot(piecewise(x< 2, 1), x = -2 .. 6)