 # Plotting in 3D. how to specify the data?

Dear Forum,
I am a completely new user to matplotlib.
I want to plot a 3D wireframe / surface plot with matplotlib. I am trying to understand how to arrange the data so that I will get the correct plot.
After trying a lot and taking reference from different examples, I wrote a code given in the filetemp.py
.
Can anyone please tell me, how can I fix it to get a correct wireframe or surface plot?
I don’t understand the array Z how it should look like.
Thank You,
Raj
temp.py

···

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I don’t think your data is well-formed. The input X, Y, and Z needs to be 2D with the same shape. I am confused by your x and y data, which you then pass into meshgrid. To illustrate, meshgrid does this:

for:
x = [1, 2, 3, 4, 5]
y = [1, 2, 3]

then the command:
X, Y = numpy.meshgrid(x, y)

produces (for X):
array([[1, 2, 3, 4, 5],
[1, 2, 3, 4, 5],
[1, 2, 3, 4, 5]])

and (for Y):

array([[1, 1, 1, 1, 1],
[2, 2, 2, 2, 2],
[3, 3, 3, 3, 3]])

Your x and y look like they are flattened versions of these. In addition, your z doesn’t seem to have enough values to fit the domain.

Ben Root

···

On Tue, Sep 27, 2011 at 11:55 AM, rajtendulkar <pranav.tendulkar@…287…> wrote:

Dear Forum,
I am a completely new user to matplotlib.
I want to plot a 3D wireframe / surface plot with matplotlib. I am trying to understand how to arrange the data so that I will get the correct plot.
After trying a lot and taking reference from different examples, I wrote a code given in the filetemp.py
.
Can anyone please tell me, how can I fix it to get a correct wireframe or surface plot?
I don’t understand the array Z how it should look like.
Thank You,
Raj
temp.py

Dear Ben,

I understood that there is problem the way plot_wireframe() function
requires the data.
However, I am trying to understand how exactly it needs the data.

For example to understand I took this random input data and did the plot -
(I took random points because in some cases it was giving me straight line)

X = np.array([[1,2,3], [4, 5, 6]])
Y = np.array([[37,85,19], [120,191,612]])
Z = np.array([[103,140,415], [16,217,718]])
ax.plot_wireframe(X, Y, Z, rstride=10, cstride=10)

And it gave me a wireframe 3D graph.
However, I have questions regarding this plot -

1. How exactly the function plot_wireframe() interprets and plots the data?
How are the co-ordinates determined?
I tried to locate the points for example (1,37,103) (2,85,140) and so on...
but I don't think it is like that.

2. why does it require multiple dimension

If my input data is -
X = np.array([1,2,3])
Y = np.array([37,85,19])
Z = np.array([103,140,415])

It gives an error ValueError: need more than 1 value to unpack

Can you please tell me about these? Regards,
Raj

Benjamin Root-2 wrote:

···

On Tue, Sep 27, 2011 at 11:55 AM, rajtendulkar > <pranav.tendulkar@...287...>wrote:

Dear Forum, I am a completely new user to matplotlib. I want to plot a 3D
wireframe / surface plot with matplotlib. I am trying to understand how
to
arrange the data so that I will get the correct plot. After trying a lot
and
taking reference from different examples, I wrote a code given in the
file
tell me, how can I fix it to get a correct wireframe or surface plot? I
don't understand the array Z how it should look like. Thank You, Raj
temp.py <http://old.nabble.com/file/p32534574/temp.py>

I don't think your data is well-formed. The input X, Y, and Z needs to be
2D with the same shape. I am confused by your x and y data, which you
then
pass into meshgrid. To illustrate, meshgrid does this:

for:
x = [1, 2, 3, 4, 5]
y = [1, 2, 3]

then the command:
X, Y = numpy.meshgrid(x, y)

produces (for X):
array([[1, 2, 3, 4, 5],
[1, 2, 3, 4, 5],
[1, 2, 3, 4, 5]])

and (for Y):
array([[1, 1, 1, 1, 1],
[2, 2, 2, 2, 2],
[3, 3, 3, 3, 3]])

Your x and y look like they are flattened versions of these. In addition,
your z doesn't seem to have enough values to fit the domain.

Ben Root

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