# Welcome to SubDivision Z-transfrom convergence checking.

This Java applet shows the convergence of the Z-transfrom of a subdivision mask a(Z).

• red     dots are the values of the mask   a(Z).
• blue   dots are the value of                    a(1)(Z)   = 2*Z / (1+Z)  * a(Z)
• green dots are the value of                    a(2)(Z)   = (2*Z)2 / (1+Z)2 * a(Z)

you should write the z-transform of the mask a(z) as a polynom of Z in the text area below the drawing area, the polynom will be calculated only when you would change the number of iterations (for now).

the parser for the polynoms text is not so soffisticated, so please try to be patint with it.

the polynom can be a sum of atoms, i.e. A0*Z^n0 + A1*Z^n1 + ... but not minus between them !!!, if you want to put a minus put it in a parenthesis, for eample insted of  X - 5, write X + (-5).

you can write the variable either as Z, z, X or x, no matter.

you can write 1*Z^1 or just Z, it's the same.

you can write multiplications, or power of polynoms, as long as it's not a minus power. for example (1+Z^2)*(1+Z)^3

please write the multiplication sign ( * ) between brackets for example (1+Z)*(1+Z^2) and not (1+Z)(1+Z^2)

the only time you can remove the multiplication sign is in the case it's an atom for example 0.5X^2 or 0.5*X^2 is the same.

You may change the number of iterations for the mask with the slider on the left.

Enjoy.