Home > Backend Development > Python Tutorial > How to plot density array using matplotlib.pyplot.contourf

How to plot density array using matplotlib.pyplot.contourf

WBOY
Release: 2024-02-12 22:27:03
forward
783 people have browsed it

如何使用 matplotlib.pyplot.contourf 绘制密度数组

Question content

I have a xarray dataset called dens and I want to plot it.

This is the data set:

<xarray.dataset>
dimensions:  (time: 641, lat: 30, lon: 30)
coordinates:
  * time     (time) datetime64[ns] 2013-07-01t12:00:00 ... 2013-08-02t12:00:00
  * lon      (lon) float64 32.73 32.83 32.94 33.05 ... 35.53 35.64 35.75 35.85
  * lat      (lat) float64 31.08 31.27 31.47 31.66 ... 36.06 36.25 36.44 36.63
data variables:
    density  (time, lat, lon) float64 2e+03 0.0 0.0 0.0 0.0 ... 0.0 0.0 0.0 0.0
Copy after login

I am using the command

plt.contourf(dens.density.values[-1,:,:]);
Copy after login

plotted it and it was working, but since I wanted the coastline to be plotted on the plot as well, I also tried using

m = basemap(llcrnrlon=data['lon'].min(), llcrnrlat=data['lat'].min(),
                urcrnrlon=data['lon'].max(), urcrnrlat=data['lat'].max(), resolution='i', suppress_ticks=1)
m.drawcoastlines();
m.fillcontinents(color='gray',lake_color='gray');
Copy after login

But when I run all the commands and then run ​​plt.show() the contour plot disappears and all it shows me is the coastline.

How to solve this problem to get a contour map in the same coastline map?

Sorry if this is a stupid question but I'm pretty new to python

thanks for your help,

Yutam

Edit: I just realized now that I was trying to combine two different "toolkits" and it is possible to do all of this using just the basemap toolkit, but just trying to write

m.contourf(dens.density.values[-1,:,:]);
Copy after login

gives me this error:

---------------------------------------------------------------------------
typeerror                                 traceback (most recent call last)
cell in[21], line 1
----> 1 m.contourf(dens.density.values[-1,:,:])

typeerror: basemap.contourf() missing 2 required positional arguments: 'y' and 'data'
Copy after login

Another edit: I keep discovering more and after reading the documentation for basemap I realized the syntax of the command should be like this

m.contourf(dens.lon.values,dens.lat.values,dens.density.values[-1,:,:]);

But now I get this error:

IndexError: too many indices for array: array is 1-dimensional, but 2 were indexed
Copy after login

I'm guessing this is because my density array is 2D, but how do I extract the density values ​​from it? I'm using [-1] in the time dimension because I actually only need the last time step

Thanks again in advance, Yotam

Last edit

This is the final plot, how can I make the surrounding land gray instead of purple? Also, is there a way to describe a larger geographic area, slightly larger, without messing up the data?

Here are the new numbers for my actual data


Correct answer


Plotting using basemaps and xarray has been discussedhere.

m = basemap(llcrnrlon=data['lon'].min(), llcrnrlat=data['lat'].min(),
            urcrnrlon=data['lon'].max(), urcrnrlat=data['lat'].max(), 
  resolution='i', suppress_ticks=1)
m.drawcoastlines();
m.fillcontinents(color='gray',lake_color='gray')
dens.density[-1,:,:].plot.contourf()
plt.show()
Copy after login

The above code should work. I use cartopy to handle features like coastlines and borders. Below is a working code snippet for you to try using the dataset.

import xarray as xr
import matplotlib.pyplot as plt
import cartopy.crs as ccrs
import cartopy.feature as cf

ds = xr.open_dataset('filename.nc')
fig = plt.figure(figsize=(8,8))
crs=ccrs.platecarree()
ax = fig.add_subplot(1,1,1, projection=crs)
gl = ax.gridlines(crs=crs, draw_labels=true,
                linewidth=0.01, color='gray', alpha=0.5, linestyle='-.')

ax.add_feature(cf.coastline.with_scale("50m"), lw=0.5)
ax.add_feature(cf.borders.with_scale("50m"), lw=0.3)

ds.density[-1,:,:].plot.contourf()
plt.show()
Copy after login

Last edit

To set all purple (zeros) to white, you can use the following cmap.

from matplotlib.colors import LinearSegmentedColormap
cm = LinearSegmentedColormap.from_list('', ['white', *plt.cm.Blues(np.arange(255))])
ds.density[-1,:,:].plot.contourf(cmap=cm)
Copy after login

The above is the detailed content of How to plot density array using matplotlib.pyplot.contourf. For more information, please follow other related articles on the PHP Chinese website!

source:stackoverflow.com
Statement of this Website
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn
Popular Tutorials
More>
Latest Downloads
More>
Web Effects
Website Source Code
Website Materials
Front End Template