[scilab-Users] 3D plot of Butterworth polynomial?

[hadi motamedi]

On 11/7/10, Ronald Michaels <ron at phenotypescreening.com> wrote:
> Hi -
>
> Assuming that you want a circular filter:
>
> Take the first equation in your link below and set a and b to 1.  Then
> set the origin of the x,y axis system to the center of your image, i.e.
> x = 0 and y = 0 at center of image.  Calculate r for each x,y pixel
> location.  Then use r in the second equation in link to find the value
> of the filter for that x,y location.  Find the equivalent position in
> image coordinates (u,v) and place filter value there in Filter array.
>
> Ron
>
>
Thank you very much for your help. Sorry do you know a free software
application that lets me to write complex mathematical expressions? It
seems that I didn't describe my case exactly so I need to write the
expression by my own and then ask you what I need to do with obtaining
such a 2-D filter?