MATLAB Central Newsreader - How to plot a graph with discrete points?

How to plot a graph with discrete points?

zedong — Mon, 21 Sep 2009 09:22:01 -0400

I have a problem on plot the graph.
I only have the following data
figgg=[x_i,y_i,z_i].
for example:
x=rand(100,1);
y=rand(100,1);
z=x.^2+y.^2;
figgg=[x,y,z];
you can use this figgg for test.
But as a matter of fact now I only have the figgg,I don't know how it's computed out. I want to plot a graph to see the 2d function.Thank you very much

Re: How to plot a graph with discrete points?

Didi Cvet — Mon, 21 Sep 2009 12:06:03 -0400

"zedong
" <zdongwu@gmail.com> wrote in message <h97gjp$k4m$1@fred.mathworks.com>...
> I have a problem on plot the graph.
> I only have the following data
> figgg=[x_i,y_i,z_i].
> for example:
> x=rand(100,1);
> y=rand(100,1);
> z=x.^2+y.^2;
> figgg=[x,y,z];
> you can use this figgg for test.
> But as a matter of fact now I only have the figgg,I don't know how it's computed out. I want to plot a graph to see the 2d function.Thank you very much

I think that this is 3D function (because you have 3 arguments)
Plot them with
>>plot3(x,y,z)

Re: How to plot a graph with discrete points?

zedong — Mon, 21 Sep 2009 14:08:03 -0400

"Didi Cvet" <didi_cvet@yahoo.com> wrote in message <h97q7b$min$1@fred.mathworks.com>...
> "zedong
> " <zdongwu@gmail.com> wrote in message <h97gjp$k4m$1@fred.mathworks.com>...
> > I have a problem on plot the graph.
> > I only have the following data
> > figgg=[x_i,y_i,z_i].
> > for example:
> > x=rand(100,1);
> > y=rand(100,1);
> > z=x.^2+y.^2;
> > figgg=[x,y,z];
> > you can use this figgg for test.
> > But as a matter of fact now I only have the figgg,I don't know how it's computed out. I want to plot a graph to see the 2d function.Thank you very much
>
> I think that this is 3D function (because you have 3 arguments)
> Plot them with
> >>plot3(x,y,z)
plot3 can only plot point.I want to plot cloudy figure.like the function trisurf.But trisurf need mesh information.I don't have mesh information

Re: How to plot a graph with discrete points?

Didi Cvet — Tue, 22 Sep 2009 10:24:19 -0400

"zedong
" <zdongwu@gmail.com> wrote in message <h981c3$9pl$1@fred.mathworks.com>...
> "Didi Cvet" <didi_cvet@yahoo.com> wrote in message <h97q7b$min$1@fred.mathworks.com>...
> > "zedong
> > " <zdongwu@gmail.com> wrote in message <h97gjp$k4m$1@fred.mathworks.com>...
> > > I have a problem on plot the graph.
> > > I only have the following data
> > > figgg=[x_i,y_i,z_i].
> > > for example:
> > > x=rand(100,1);
> > > y=rand(100,1);
> > > z=x.^2+y.^2;
> > > figgg=[x,y,z];
> > > you can use this figgg for test.
> > > But as a matter of fact now I only have the figgg,I don't know how it's computed out. I want to plot a graph to see the 2d function.Thank you very much
> >
> > I think that this is 3D function (because you have 3 arguments)
> > Plot them with
> > >>plot3(x,y,z)
> plot3 can only plot point.I want to plot cloudy figure.like the function trisurf.But trisurf need mesh information.I don't have mesh information

I'm not sure but try this:

[xx yy]=meshgrid(rand(100,1));
>> zz=xx.^2+yy.^2;
>> surfc(xx,yy,zz)
>> surf(xx,yy,zz)
>> mesh(xx,yy,zz)
one of those plot functions might help you.

Re: How to plot a graph with discrete points?

zedong — Tue, 22 Sep 2009 11:07:04 -0400

"Didi Cvet" <didi_cvet@yahoo.com> wrote in message <h9a8kj$ru6$1@fred.mathworks.com>...
> "zedong
> " <zdongwu@gmail.com> wrote in message <h981c3$9pl$1@fred.mathworks.com>...
> > "Didi Cvet" <didi_cvet@yahoo.com> wrote in message <h97q7b$min$1@fred.mathworks.com>...
> > > "zedong
> > > " <zdongwu@gmail.com> wrote in message <h97gjp$k4m$1@fred.mathworks.com>...
> > > > I have a problem on plot the graph.
> > > > I only have the following data
> > > > figgg=[x_i,y_i,z_i].
> > > > for example:
> > > > x=rand(100,1);
> > > > y=rand(100,1);
> > > > z=x.^2+y.^2;
> > > > figgg=[x,y,z];
> > > > you can use this figgg for test.
> > > > But as a matter of fact now I only have the figgg,I don't know how it's computed out. I want to plot a graph to see the 2d function.Thank you very much
> > >
> > > I think that this is 3D function (because you have 3 arguments)
> > > Plot them with
> > > >>plot3(x,y,z)
> > plot3 can only plot point.I want to plot cloudy figure.like the function trisurf.But trisurf need mesh information.I don't have mesh information
>
>
> I'm not sure but try this:
>
> [xx yy]=meshgrid(rand(100,1));
> >> zz=xx.^2+yy.^2;
> >> surfc(xx,yy,zz)
> >> surf(xx,yy,zz)
> >> mesh(xx,yy,zz)
> one of those plot functions might help you.
Yes ,You are right.But I now only have the data [x_i,y_i,z_i],I don't have the structure.surf need z be a matrix but my z is a vector.Thank you

Re: How to plot a graph with discrete points?

arich82 — Wed, 23 Sep 2009 09:19:03 -0400

> > > > > I only have the following data
> > > > > figgg=[x_i,y_i,z_i].
> > > > > for example:
> > > > > x=rand(100,1);
> > > > > y=rand(100,1);
> > > > > z=x.^2+y.^2;
> > > > > figgg=[x,y,z];
> > > > > you can use this figgg for test.

> Yes ,You are right.But I now only have the data [x_i,y_i,z_i],I don't have the structure.surf need z be a matrix but my z is a vector.Thank you

Is this what you're looking for?

tri = delaunay(x,y);
h = trisurf(tri, x, y, z);

See <http://www.mathworks.com/matlabcentral/fx_files/5105/1/content/surf_from_scatter.html>, and maybe <http://www.mathworks.com/matlabcentral/fileexchange/8998>.

Re: How to plot a graph with discrete points?

zedong — Tue, 13 Oct 2009 14:36:04 -0400

"arich82 " <|a|r|i|c|8|2|@hotmail.com> wrote in message <h9cp67$t60$1@fred.mathworks.com>...
> > > > > > I only have the following data
> > > > > > figgg=[x_i,y_i,z_i].
> > > > > > for example:
> > > > > > x=rand(100,1);
> > > > > > y=rand(100,1);
> > > > > > z=x.^2+y.^2;
> > > > > > figgg=[x,y,z];
> > > > > > you can use this figgg for test.
>
> > Yes ,You are right.But I now only have the data [x_i,y_i,z_i],I don't have the structure.surf need z be a matrix but my z is a vector.Thank you
>
>
>
> Is this what you're looking for?
>
> tri = delaunay(x,y);
> h = trisurf(tri, x, y, z);
>
> See <http://www.mathworks.com/matlabcentral/fx_files/5105/1/content/surf_from_scatter.html>, and maybe <http://www.mathworks.com/matlabcentral/fileexchange/8998>.

Thank you very much.That must be the best solution.I have never thought about it.Very beautiful