`f(x; a, b) = a/b(x/b)^(a-1)e^(-(x/b)^a)`
`a` : shape parameter
`b` : scale parameter
`f(x; a, b, r, m) = a/b((x-r)/b)^(a-1)e^(-((x-r)/b)^a)m`
`a` : shape parameter
`b` : scale parameter
`r` : location parameter. It shifts the graph to left or right.
`m` : magnification of vertical axis. It simply multiply the vertical axis values.
`f(x; a1, b1, a2, b2, r, m, c) = (c((a1)/(b1)((x-r)/(b1))^(a1-1)e^(-((x-r)/(b1))^(a1))) + (1-c)((a2)/(b2)((x-r)/(b2))^(a2-1)e^(-((x-r)/(b2))^(a2))))m`
`a1` : shape parameter of first component
`b1` : scale parameter of first component
`a2` : shape parameter of second component
`b2` : scale parameter of second component
`r` : location parameter. It shifts the graph to left or right.
`m` : magnification of vertical axis. It simply multiply the vertical axis values.
`c` : component ratio