I am trying to view a basic polygon read from a Shapefile using matplotlib and pyshp
But all my efforts yield just an empty axes with no polygon. Here are few of my tries, using the dataset showing the borders of Belgium:
import shapefile as sf
r = sf.Reader("BEL_adm/BEL_adm0")
p=r.shapes()
b=p[0]
points = b.points
import matplotlib.pyplot as plt
from matplotlib.path import Path
imporst matplotlib.patches as patches
verts = points
verts = []
for x,y in points:
verts.append(tuple([x,y]))
codes = ['']*len(verts)
codes[0] = Path.MOVETO
codes[-1] = Path.CLOSEPOLY
for i in range(1,len(verts)):
codes[i]=Path.LINETO
path = Path(verts, codes)
fig = plt.figure()
ax = fig.add_subplot(111)
patch = patches.PathPatch(path, facecolor='orange', lw=2)
ax.add_patch(patch)
ax.set_xlim(-2,2)
ax.set_ylim(-2,2)
plt.show()
Another try with patches also yields an empty frame:
fig = plt.figure(figsize=(11.7,8.3))
ax = plt.subplot(111)
x,y=zip(*b.points)
import matplotlib.patches as patches
import matplotlib.pyplot as plt
bol=patches.Polygon(b.points,True, transform=ax.transAxes)
ax.add_patch(bol)
ax.set_ylim(0,60)
ax.set_xlim(0,200)
plt.show()
Would be happy to see what I am missing.
Thanks, Oz
instead of calling set_xlim(), set_ylim() to set the range of axis, you can use ax.autoscale().
For your Polygon version, you don't need to set transform argument to ax.transAxes, just call:
bol=patches.Polygon(b.points,True)
Related
I wanted to rotate a Rectangle in matplotlib but when I apply the transformation, the rectangle doesn't show anymore:
rect = mpl.patches.Rectangle((0.0120,0),0.1,1000)
t = mpl.transforms.Affine2D().rotate_deg(45)
rect.set_transform(t)
is this a known bug or do I make a mistake?
The patch in the provided code makes it hard to tell what's going on, so I've made a clear demonstration that I worked out from a matplotlib example:
import numpy as np
import matplotlib.pyplot as plt
import matplotlib.patches as patches
import matplotlib as mpl
fig = plt.figure()
ax = fig.add_subplot(111)
r1 = patches.Rectangle((0,0), 20, 40, color="blue", alpha=0.50)
r2 = patches.Rectangle((0,0), 20, 40, color="red", alpha=0.50)
t2 = mpl.transforms.Affine2D().rotate_deg(-45) + ax.transData
r2.set_transform(t2)
ax.add_patch(r1)
ax.add_patch(r2)
plt.xlim(-20, 60)
plt.ylim(-20, 60)
plt.grid(True)
plt.show()
Apparently the transforms on patches are composites of several transforms for dealing with scaling and the bounding box. Adding the transform to the existing plot transform seems to give something more like what you'd expect. Though it looks like there's still an offset to work out.
import numpy as np
import matplotlib.pyplot as plt
import matplotlib.patches as patches
import matplotlib as mpl
fig = plt.figure()
ax = fig.add_subplot(111)
rect = patches.Rectangle((0.0120,0),0.1,1000)
t_start = ax.transData
t = mpl.transforms.Affine2D().rotate_deg(-45)
t_end = t_start + t
rect.set_transform(t_end)
print repr(t_start)
print repr(t_end)
ax.add_patch(rect)
plt.show()
I have trouble with the ortho projection and pcolormesh.
It should plot a mesh of grid points. Instead, in the upper right portion of the sphere it plots strange lines instead of grid points. The mapping of the mesh looks off.
I tried the code below.
from mpl_toolkits.basemap import Basemap
import numpy as np
import matplotlib.pyplot as plt
plt.clf()
dpp =1 # degrees per pixel
lons = np.arange(-180,180+dpp,dpp)
lats = -1*np.arange(-90,90+dpp,dpp)
m = Basemap(projection='ortho', lon_0=0, lat_0=-60, resolution='l')
data = np.random.random((np.size(lats), np.size(lons)))
lons, lats = np.meshgrid(lons, lats)
x, y = m(lons, lats)
im = m.pcolormesh(x, y, data, latlon=False, cmap='RdBu')
#im = m.pcolormesh(lons, lats, data, latlon=True, cmap='RdBu')
m.colorbar(im)
plt.show()
I obtain the following plot:
The random noise should be mapped onto the entire sphere, but there is clearly an error in the upper right of the ortho map.
Does anyone else get this error with the included code?
Since basemap would require you to manually filter out unwanted data (those that are "behind the globe"), here is how to do the same with cartopy.
import numpy as np
import matplotlib.pyplot as plt
import cartopy.crs as ccrs
proj = ccrs.Orthographic(central_longitude=0.0, central_latitude=-60.0)
plt.figure(figsize=(3, 3))
ax = plt.axes(projection=proj)
dpp =1
lons = np.arange(-180,180+dpp,dpp)
lats = 1*np.arange(-90,90+dpp,dpp)
data = np.random.random((np.size(lats), np.size(lons)))
lons, lats = np.meshgrid(lons, lats)
im = ax.pcolormesh(lons, lats, data, cmap='RdBu', transform=ccrs.PlateCarree())
ax.coastlines(resolution='110m')
ax.gridlines()
plt.show()
A fix to Basemap was suggested in the github basemap thread here
I have a shapefile that maps the world to sales territories. The shapefile records lists the sales territory code and name. I would like to be able to add the territory code in the center of the region, but to do using ax.text, I need the center point of the region. Any ideas how to do this?
import matplotlib.pyplot as plt
import pandas as pd
import numpy as np
import shapefile
from mpl_toolkits.basemap import Basemap as Basemap
from matplotlib.colors import rgb2hex, Normalize
from matplotlib.patches import Polygon
from matplotlib.colorbar import ColorbarBase
from matplotlib.collections import PatchCollection
plt.rcParams['figure.figsize'] = [16,12]
fig = plt.figure()
m = Basemap(llcrnrlon=-121,llcrnrlat=20,urcrnrlon=-62,urcrnrlat=51,
projection='lcc',lat_1=32,lat_2=45,lon_0=-95)
shp_info = m.readshapefile('world_countries_boundary_file_world_2002','countries',drawbounds=True)
sf = shapefile.Reader('territory_map') # Custom file mapping out territories
recs = sf.records()
shapes = sf.shapes()
Nshp = len(shapes)
colors={}
territory_codes=[]
cmap = plt.cm.RdYlGn
# details is a pandas datafile with column "DELTA" that has data to plot
vmin = details.DELTA.min()
vmax = details.DELTA.max()
norm = Normalize(vmin=vmin, vmax=vmax)
for index,row in details.iterrows():
colors[row['TERRITORY_CODE']] = cmap((row['DELTA']-vmin)/(vmax-vmin))[:3]
territory_codes.append(row['TERRITORY_CODE'])
ax = fig.add_subplot(111)
for nshp in range(Nshp):
ptchs = []
pts = np.array((shapes[nshp].points))
prt = shapes[nshp].parts
par = list(prt) + [pts.shape[0]]
for pij in range(len(prt)):
ptchs.append(Polygon(pts[par[pij]:par[pij+1]]))
try:
color = rgb2hex(colors[recs[nshp][0]])
except:
color = 'w' # If no data, leave white (blank)
ax.add_collection(PatchCollection(ptchs, facecolor=color, edgecolor='b', linewidths=.7))
x, y = # Coordinates that are center of region
ax.text(x, y, recs[nshp][0]) # <---- this would be the text to add
# Add colorbar
ax_c = fig.add_axes([0.1, 0.1, 0.8, 0.02])
cb = ColorbarBase(ax_c,cmap=cmap,norm=norm,orientation='horizontal')
cb.ax.set_xlabel('Daily Change, USD')
#Set view to United States
ax.set_xlim(-150,-40)
ax.set_ylim(15,70)
plt.show()
Resulting Map of Code without Territory Names
you're probably looking to take the mean of all the x coordinates and the mean of all the y coordinates of your polygon shape.
I can't test this but it could look something like this:
x,y = pts[0].mean(), pts[1].mean()
or this:
x,y = pts[:,0].mean(), pts[:,1].mean()
depending on the dimensions of your numpy array.
I am trying to shorten a colorbar by half. Does anyone know how to do this? I tried cax.get_position() and then cax.set_position(), but this method did not work.
Besides, it seems that axes created by axes_grid1 has the same bbox positions as the original axes. Is this a bug?
PS. I have to use axes_grid1 to create colorbar axes, because I need to use tight_layout() afterwards, and tight_layout() only applies to axes created by axes_grid1 but not ones created by add_axes().
import matplotlib.pyplot as plt
from mpl_toolkits.axes_grid1 import make_axes_locatable
import numpy as np
plt.figure()
ax = plt.gca()
im = ax.imshow(np.arange(100).reshape((10,10)))
divider = make_axes_locatable(ax)
cax = divider.append_axes("right", size="5%", pad=0.05)
bbox1 = ax.get_position()
print(bbox1)
bbox1 = cax.get_position()
print(bbox1)
plt.colorbar(im, cax=cax)
plt.show()
The whole point of the axes_divider is to divide the axes to make space for a new axes. This ensures that all axes have the same surrounding box. And that is the box you see being printed.
Some of the usual ways to create a colorbar, at a certain location in the figue are shown in this question. Here the problem seems to be to be able to call tight_layout. This is achievable with the following two options. (There might be others still.)
A. using gridspec
I'm not too sure about the exact requirements here, but it seems that using a normal grid layout would be more in the direction of what you need here.
import numpy as np
import matplotlib.pyplot as plt
import matplotlib.gridspec as gridspec
fig = plt.figure()
gs = gridspec.GridSpec(2, 2, width_ratios=[95,5],)
ax = fig.add_subplot(gs[:, 0])
im = ax.imshow(np.arange(100).reshape((10,10)))
cax = fig.add_subplot(gs[1, 1])
fig.colorbar(im, cax=cax, ax=ax)
plt.tight_layout()
plt.show()
B. Using axes_grid1
If you really need to use axes_grid1, it might become a little bit more complicated.
import matplotlib.pyplot as plt
import matplotlib.axes
from mpl_toolkits.axes_grid1 import make_axes_locatable, Size
import numpy as np
fig, ax = plt.subplots()
im = ax.imshow(np.arange(100).reshape((10,10)))
divider = make_axes_locatable(ax)
pad = 0.03
pad_size = Size.Fraction(pad, Size.AxesY(ax))
xsize = Size.Fraction(0.05, Size.AxesX(ax))
ysize = Size.Fraction(0.5-pad/2., Size.AxesY(ax))
divider.set_horizontal([Size.AxesX(ax), pad_size, xsize])
divider.set_vertical([ysize, pad_size, ysize])
ax.set_axes_locator(divider.new_locator(0, 0, ny1=-1))
cax = matplotlib.axes.Axes(ax.get_figure(),
ax.get_position(original=True))
locator = divider.new_locator(nx=2, ny=0)
cax.set_axes_locator(locator)
fig.add_axes(cax)
fig.colorbar(im, cax=cax)
plt.tight_layout()
plt.show()
If you want to insert a small plot inside a bigger one you can use Axes, like here.
The problem is that I don't know how to do the same inside a subplot.
I have several subplots and I would like to plot a small plot inside each subplot.
The example code would be something like this:
import numpy as np
import matplotlib.pyplot as plt
fig = plt.figure()
for i in range(4):
ax = fig.add_subplot(2,2,i)
ax.plot(np.arange(11),np.arange(11),'b')
#b = ax.axes([0.7,0.7,0.2,0.2])
#it gives an error, AxesSubplot is not callable
#b = plt.axes([0.7,0.7,0.2,0.2])
#plt.plot(np.arange(3),np.arange(3)+11,'g')
#it plots the small plot in the selected position of the whole figure, not inside the subplot
Any ideas?
I wrote a function very similar to plt.axes. You could use it for plotting yours sub-subplots. There is an example...
import matplotlib.pyplot as plt
import numpy as np
#def add_subplot_axes(ax,rect,facecolor='w'): # matplotlib 2.0+
def add_subplot_axes(ax,rect,axisbg='w'):
fig = plt.gcf()
box = ax.get_position()
width = box.width
height = box.height
inax_position = ax.transAxes.transform(rect[0:2])
transFigure = fig.transFigure.inverted()
infig_position = transFigure.transform(inax_position)
x = infig_position[0]
y = infig_position[1]
width *= rect[2]
height *= rect[3] # <= Typo was here
#subax = fig.add_axes([x,y,width,height],facecolor=facecolor) # matplotlib 2.0+
subax = fig.add_axes([x,y,width,height],axisbg=axisbg)
x_labelsize = subax.get_xticklabels()[0].get_size()
y_labelsize = subax.get_yticklabels()[0].get_size()
x_labelsize *= rect[2]**0.5
y_labelsize *= rect[3]**0.5
subax.xaxis.set_tick_params(labelsize=x_labelsize)
subax.yaxis.set_tick_params(labelsize=y_labelsize)
return subax
def example1():
fig = plt.figure(figsize=(10,10))
ax = fig.add_subplot(111)
rect = [0.2,0.2,0.7,0.7]
ax1 = add_subplot_axes(ax,rect)
ax2 = add_subplot_axes(ax1,rect)
ax3 = add_subplot_axes(ax2,rect)
plt.show()
def example2():
fig = plt.figure(figsize=(10,10))
axes = []
subpos = [0.2,0.6,0.3,0.3]
x = np.linspace(-np.pi,np.pi)
for i in range(4):
axes.append(fig.add_subplot(2,2,i))
for axis in axes:
axis.set_xlim(-np.pi,np.pi)
axis.set_ylim(-1,3)
axis.plot(x,np.sin(x))
subax1 = add_subplot_axes(axis,subpos)
subax2 = add_subplot_axes(subax1,subpos)
subax1.plot(x,np.sin(x))
subax2.plot(x,np.sin(x))
if __name__ == '__main__':
example2()
plt.show()
You can now do this with matplotlibs inset_axes method (see docs):
from mpl_toolkits.axes_grid.inset_locator import inset_axes
inset_axes = inset_axes(parent_axes,
width="30%", # width = 30% of parent_bbox
height=1., # height : 1 inch
loc=3)
Update: As Kuti pointed out, for matplotlib version 2.1 or above, you should change the import statement to:
from mpl_toolkits.axes_grid1.inset_locator import inset_axes
There is now also a full example showing all different options available.
From matplotlib 3.0 on, you can use matplotlib.axes.Axes.inset_axes:
import numpy as np
import matplotlib.pyplot as plt
fig, axes = plt.subplots(2,2)
for ax in axes.flat:
ax.plot(np.arange(11),np.arange(11))
ins = ax.inset_axes([0.7,0.7,0.2,0.2])
plt.show()
The difference to mpl_toolkits.axes_grid.inset_locator.inset_axes mentionned in #jrieke's answer is that this is a lot easier to use (no extra imports etc.), but has the drawback of being slightly less flexible (no argument for padding or corner locations).
source: https://matplotlib.org/examples/pylab_examples/axes_demo.html
from mpl_toolkits.axes_grid.inset_locator import inset_axes
import matplotlib.pyplot as plt
import numpy as np
# create some data to use for the plot
dt = 0.001
t = np.arange(0.0, 10.0, dt)
r = np.exp(-t[:1000]/0.05) # impulse response
x = np.random.randn(len(t))
s = np.convolve(x, r)[:len(x)]*dt # colored noise
fig = plt.figure(figsize=(9, 4),facecolor='white')
ax = fig.add_subplot(121)
# the main axes is subplot(111) by default
plt.plot(t, s)
plt.axis([0, 1, 1.1*np.amin(s), 2*np.amax(s)])
plt.xlabel('time (s)')
plt.ylabel('current (nA)')
plt.title('Subplot 1: \n Gaussian colored noise')
# this is an inset axes over the main axes
inset_axes = inset_axes(ax,
width="50%", # width = 30% of parent_bbox
height=1.0, # height : 1 inch
loc=1)
n, bins, patches = plt.hist(s, 400, normed=1)
#plt.title('Probability')
plt.xticks([])
plt.yticks([])
ax = fig.add_subplot(122)
# the main axes is subplot(111) by default
plt.plot(t, s)
plt.axis([0, 1, 1.1*np.amin(s), 2*np.amax(s)])
plt.xlabel('time (s)')
plt.ylabel('current (nA)')
plt.title('Subplot 2: \n Gaussian colored noise')
plt.tight_layout()
plt.show()