[Scilab-users] Problems with plot 3d. Function fplot3d

[Ubirajara Marques da Cruz]

To user support,

Recently I was studing a function that i wanted to plot it. This function is a 3d equation that I wrote above:

[cid:image004.png at 01CE63A6.F58C59E0]
I try to use fplot3d to plot following interval x=0:0.01:1 and y=0:0.01:3.
When I analise the results this function has positive and negative numbers to plot but when i plot it it only show positive numbers.

I look for the answers about square root of negative numbers and i found help tips that show into this case the answer is a complex number.  Then I see that matrix z is a vector that has real numbers and complex numbers(they are mixed) and fplot3d shows a result very diferente of I was expecting.

If point is a real number fplot3d plot right surface and if the point is a complex number it shows a wrong surface. What must i do to solve this problem?

Follow, I send code that I´ve been use into scilab 4.1.2 (scipad)

x=0:0.01:1 ;y=0:0.01:3
deff('z=f(x,y)','z=( (1-exp(-5*x))-y)^(1/3)')
clf()
fplot3d(x,y,f,alpha=60,theta=60)

[cid:image007.jpg at 01CE63A6.F58C59E0]

Down part of this graphic is mirrored to up side and values are wrong. The right result that i was expecting is the surface to be drawnt to negative side.

Thank you for yours helps.

Ubirajara Marques da Cruz
Engenheiro de Projetos Elétricos
Gerência de Engenharia Eletromecânica de Expansão da Geração e de Fontes Alternativas
Diretoria de Geração e Transmissão
Companhia Energética de Minas Gerais - Cemig
Telefone: 55 (31) 3506-4602
Email: biracruz at cemig.com.br
www.cemig.com.br<http://www.cemig.com.br>
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