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How plot a shifted Parabola?

Asked by Ali on 4 Mar 2011

I know Parabola have formula z=x^2+y^2 now I want to plot it when it has simple shifted like image: http://i55.tinypic.com/33y50kx.gif I know how to plot3 or surf but I don't know how to plot3 this one.

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Ali

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2 Answers

Answer by Paulo Silva on 4 Mar 2011
plot3(X+10,Y+10,Z); %this shifts the parabola 10 units on both x and y axis

2 Comments

Ali on 5 Mar 2011

Please check out this
http://www.mathhelpforum.com/math-help/f43/parabola-polar-coordinates-173404.html
I need this type of shifting!

Paulo Silva on 5 Mar 2011

That's more like rotation than shifting.

Paulo Silva
Answer by Paulo Silva on 5 Mar 2011
x=-10:0.1:10;
y=x;
z=x.^2+y.^2;
ang=pi/4;
sm=[cos(ang) 0 sin(ang)
    0  1  0
   -sin(ang) 0 cos(ang)];
r=sm*[x;y;z];
x=r(1,:);y=r(2,:);z=r(3,:);
[x,y]=meshgrid(x,y);
plot3(x,y,z)

1 Comment

Ali on 5 Mar 2011

Rotation is better!
what you code is not what I want.
My code:
clc
clear all
spi=sin(pi/4);
cpi=cos(pi/4);
f=0:pi/20:pi;
t=0:(2*pi)/20:2*pi;
[F T]=meshgrid(f,t);
x=sin(F).*cos(T);
y=sin(F).*sin(T);
z=(x.^2+y.^2);
w=[cpi 0 -spi;0 1 0;spi 0 cpi];
surf(x,y,z);
This code just draw Parabola without rotation how can I do w*[x,y,z]??

Paulo Silva

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