I have just installed vtk, mayavi. Then I ran an example, but nothing showed. Can you tell me how to show the figure?
import mayavi.mlab as mlab
import numpy as np
import vtk
x, y, z, value = np.random.random((4, 40))
mlab.points3d(x, y, z, value)
As described in the documentation, see here, you need to call mlab.show() when running such a script after your mlab.points3d().
Related
I am a beginner to Python and experimenting with a plot. the script runs fine but plot does not show up.
the matplotlib and numpy libraries are installed.
import numpy as np
f= h5py.File('3DIMG_05JUN2021_0000_L3B_HEM_DLY.h5','r')
#Studying the structure of the file by printing what HDF5 groups are present
for key in f.keys():
print(key) #Names of the groups in HDF5 file.
# will print the variables in the file
#Get the HDF5 group
ls=list(f.keys())
print("ls")
print(ls)
tsurf = f['HEM_DLY'][:]
print("tsurf")
print(tsurf)
tsurf1=np.squeeze(tsurf)
print(tsurf1.shape)
import matplotlib.pyplot as plt
im= plt.plot(tsurf1)
#plt.colorbar()
plt.imshow(im)```
Python version is 3 running on Ubuntu
Difficult to give you the exact answer without the dataset (please update the question with the dataset), but for sure, plt.plot does not return an object that can be plotted with plt.imshow
Try instead:
ax = plt.plot(tsurf1)
plt.show()
Probably the error was on the final plot.Try this:
import numpy as np
import matplotlib.pyplot as plt
f= h5py.File('/path','r')
ls=list(f.keys())
tsurf = f['your_key_str'][:]
tsurf1=np.squeeze(tsurf)
im= plt.plot(tsurf1)
plt.show(im) # <-- plt.show() NOT plt.imshow()
I am just looking for some kind of working example which will allow me to have a slider and a sine wave plot whereby I can vary the frequency in a Jupyter Notebook. All the online demos that I have Googled don't work for me. The issue seems to be that the old matplotlib graph is not erased before the new one is created.
Here is my minimal example
import ipywidgets as widgets
from IPython.display import display, clear_output
import matplotlib.pyplot as plt
import numpy as np
def f(a):
clear_output(wait=True)
fig, ax = plt.subplots()
x = np.linspace(0, 2*np.pi, 100)
y = np.sin(a*x)
ax.grid()
ax.set_xlabel("x")
ax.set_ylabel("y")
ax.plot(x,y)
ax.set_title("y = sin(x)")
%matplotlib inline
from time import sleep
for i in range(1,10):
clear_output(wait=True)
f(i)
sleep(1)
I have also tried
out = widgets.Output(layout={'border': '1px solid black'})
with out:
widgets.interact(f, a=1)
out.clear_output()
display(out)
However nothing I try will erase the previous matplotlib graph. They just all pile up on top of each other. I admit I am floundering as I don't really understand the API that well and the example in the documentation don't work for me.
I don't expect people to fix my code as it is probably rubbish. I am just looking for a working example which will allow me to interactively control the frequency and redraw the sine wave on a Jupyter notebook.
Here is a minimal example that works for me:
from ipywidgets import interact
import ipywidgets as widgets
import matplotlib.pyplot as plt
import numpy as np
def plot(freq):
x = np.linspace(0, 2*np.pi)
y = np.sin(x * freq)
plt.plot(x, y)
interact(plot, freq = widgets.FloatSlider(value=2, min=0.1, max=5, step=0.1))
default plot:
Screenshot of notebook after moving the slider to the right:
I'm trying to transform the scales on y-axis to the log values. For example, if one of the numbers on y is 0.01, I want to get -2 (which is log(0.01)). How should I do this in matplotlib (or any other library)?!
Thanks,
Without plt.yscale('log') there will be few y-ticks visible that have a nice number as log. You can change the "formatter" to a function that only shows the exponent. Also note that in the latest seaborn version distplot has been replaced by histplot(..., kde=True) or kdeplot(...).
Here is an example:
import matplotlib.pyplot as plt
from matplotlib.ticker import LogFormatterExponent
import numpy as np
import seaborn as sns
x = np.random.randn(10, 1000).cumsum(axis=1).ravel()
ax = sns.histplot(x, kde=True, stat='density', color='purple')
ax.set_yscale('log')
ax.yaxis.set_major_formatter(LogFormatterExponent(base=10.0, labelOnlyBase=True))
ax.set_ylabel(ax.get_ylabel() + ' (exponent)')
ax.margins(x=0)
plt.show()
I am writting a very simple script, one that plot a sin using jupyter notebook (python 3). when I put:
import numpy
import matplotlib.pyplot as plt
x=np.arange(0.0,5*np.pi,0.001)
y = np.sin(x)
plt.plot(x,y)
The plot is fine.
However if :
import numpy
import matplotlib.pyplot as plt
x=np.arange(0.0,5*np.pi,0.001)
np.random.shuffle(x)
y = np.sin(x)
plt.plot(x,y)
the image is
I don't understand why shuffling the x BEFORE I ran sin does it.
thank you
Let's first simplify things a bit. We plot 4 points and annote them with the order in which they are plotted.
import numpy as np; np.random.seed(42)
import matplotlib.pyplot as plt
x=np.arange(4)
y = np.sin(x)
plt.plot(x,y, marker="o")
for i, (xi,yi) in enumerate(zip(x,y)):
plt.annotate(str(i), xy=(xi,yi), xytext=(0,4),
textcoords="offset points", ha="center")
plt.show()
No if we shuffle x and plot the same graph,
x=np.arange(4)
np.random.shuffle(x)
y = np.sin(x)
we see that positions of the points are still are the same, but while e.g. previously the first point was the one at (0,0), it's now the third one appearing there. Due to this randomized order, the connecting lines go zickzack.
Now if you use enough points, all those lines will add up to look like a complete surface, which is what you get in your image.
When I try to obtain plots in which the axis (both formulae and text) are written in LaTeX standard roman font, I keep not obtaining the plot, but the code runs without warnings. In particular, this simple scatter with TeX code in the axis labels, in which I have put my better understanding of the documentation:
import numpy as np
import matplotlib.pyplot as plt
from matplotlib import rc
x = np.linspace(0,1,100)
y = np.random.rand(100,1)
plt.rc('text', usetex=True)
plt.rc('font', family='roman')
plt.scatter(x, y, c='b', s=10)
plt.xlabel(r'$\lambda$ ($\AA$)',size='12')
plt.ylabel(r'$F_\alpha (W/m^2)$ ',size='12')
plt.title(r'A title in \LaTeX typography')
plt.show()
keeps yielding a message like <matplotlib.figure.Figure at 0x1f75d4750>, which I have met before, but I keep failing when trying to remedy this one. In addition, saving the plot (png or pdf) would not solve the issue, and if the problem is related to TeX, I have definitely not found any resource that can help. I use MacOS Sierra.