[Scilab-users] Symbolic computation in Scilab

[Pablo Fonovich]

Hi:
I assume that you wanted to calculate the z-transfor of the difference of 7*x1 and 6*x2... And for the limits of your sumation, i also assume your sequence is causal...
In theory, if im not making a mistake, X1(z) should be 1/(1-0.33*z^(-1)) and X2(z)=1/(1-0.5*z^(-1))...

If this is right, the answer should be the difference between them, scaled by 7 and 6 respectively...

If i do the calculations with maxima i get the expected result...

However, as i think i told you before, maxima asks for some convergence conditions...

For example, when i try to do the first summation it ask if |z|-0.33 is positive, negative or zero... this is like giving the ROC of the z transfor, that in this case is |z|>0.33 so you have to answer "p" for positive...

I don't know is scilab with the scimax toolbox asked for this convergence conditions... but i think that that is the problem yo are having... remebmer that if |z|<a for the sequence a^n*u(n), then the summation does not converge...

I don't have scimax toolbox installed, so i can't tell you how to continue with it... but with maxima alone the result is ok..

what happens if you try to disp(x1) and disp(x2)?? are they ok?? 





 

> Date: Fri, 14 Aug 2015 19:29:36 -0700
> From: doole93 at gmail.com
> To: users at lists.scilab.org
> Subject: Re: [Scilab-users] Symbolic computation in Scilab
> 
> Another thing i wanted to ask. When executing a script such as this
> Syms n z ;
> x1 =(0.33) ^( n )
> X1 = %sym_sum (7* x1 *( z ^( - n ) ) ,n ,0 , %inf )
> x2 =(0.5) ^( n )
> X2 = %sym_sum (6* x2 *( z ^( - n ) ) ,n ,0 , %inf )
> X = X1 - X2
> disp (X , 'a n s=' )
> 
> i get something like this
> 
> a n s=   
>  
>                 %inf            %inf
>                 ====      n     ====     n
>                 \     0.33      \     0.5
>               7  >    ----- - 6  >    ----
>                 /       n       /       n
>                 ====   z        ====   z
>                 n = 0           n = 0
> 
> Since I'm a newbie in Scilab, and I'm also not particularly good with the
> mathematical background of the z-transformation (I'm still learning it), is
> this the output I should be getting from the sequence of commands above?
> 
> 
> 
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