|
10 | 10 | # sphinx_gallery_thumbnail_number = 2 |
11 | 11 |
|
12 | 12 | importnumpyasnp |
13 | | -fromscipy.interpolateimportsplprep,splev |
14 | 13 |
|
15 | 14 | importmatplotlib.pyplotasplt |
16 | 15 | frommatplotlib.pathimportPath |
|
22 | 21 | x,y=r*np.cos(t),r*np.sin(t) |
23 | 22 |
|
24 | 23 | fig,ax=plt.subplots() |
25 | | -ax.plot(x,y) |
26 | | -plt.show() |
| 24 | +ax.plot(x,y,"k") |
| 25 | +ax.set(aspect=1) |
27 | 26 |
|
28 | 27 | ############################################################################# |
29 | 28 | # An error band can be used to indicate the uncertainty of the curve. |
|
39 | 38 | # `~.Axes.fill_between` method (see also |
40 | 39 | # :doc:`/gallery/lines_bars_and_markers/fill_between_demo`). |
41 | 40 |
|
42 | | -# Error amplitudes depending on the curve parameter *t* |
43 | | -# (actual values are arbitrary and only for illustrative purposes): |
44 | | -err=0.05*np.sin(2*t)**2+0.04+0.02*np.cos(9*t+2) |
45 | 41 |
|
46 | | -# calculate normals via derivatives of splines |
47 | | -tck,u=splprep([x,y],s=0) |
48 | | -dx,dy=splev(u,tck,der=1) |
49 | | -l=np.hypot(dx,dy) |
50 | | -nx=dy/l |
51 | | -ny=-dx/l |
| 42 | +defdraw_error_band(ax,x,y,err,**kwargs): |
| 43 | +# Calculate normals via centered finite differences (except the first point |
| 44 | +# which uses a forward difference and the last point which uses a backward |
| 45 | +# difference). |
| 46 | +dx=np.concatenate([[x[1]-x[0]],x[2:]-x[:-2], [x[-1]-x[-2]]]) |
| 47 | +dy=np.concatenate([[y[1]-y[0]],y[2:]-y[:-2], [y[-1]-y[-2]]]) |
| 48 | +l=np.hypot(dx,dy) |
| 49 | +nx=dy/l |
| 50 | +ny=-dx/l |
52 | 51 |
|
53 | | -# end points of errors |
54 | | -xp=x+nx*err |
55 | | -yp=y+ny*err |
56 | | -xn=x-nx*err |
57 | | -yn=y-ny*err |
| 52 | +# end points of errors |
| 53 | +xp=x+nx*err |
| 54 | +yp=y+ny*err |
| 55 | +xn=x-nx*err |
| 56 | +yn=y-ny*err |
58 | 57 |
|
59 | | -vertices=np.block([[xp,xn[::-1]], |
60 | | - [yp,yn[::-1]]]).T |
61 | | -codes=Path.LINETO*np.ones(len(vertices),dtype=Path.code_type) |
62 | | -codes[0]=codes[len(xp)]=Path.MOVETO |
63 | | -path=Path(vertices,codes) |
| 58 | +vertices=np.block([[xp,xn[::-1]], |
| 59 | + [yp,yn[::-1]]]).T |
| 60 | +codes=np.full(len(vertices),Path.LINETO) |
| 61 | +codes[0]=codes[len(xp)]=Path.MOVETO |
| 62 | +path=Path(vertices,codes) |
| 63 | +ax.add_patch(PathPatch(path,**kwargs)) |
64 | 64 |
|
65 | | -patch=PathPatch(path,facecolor='C0',edgecolor='none',alpha=0.3) |
66 | 65 |
|
67 | | -fig,ax=plt.subplots() |
68 | | -ax.plot(x,y) |
69 | | -ax.add_patch(patch) |
| 66 | +axs= (plt.figure(constrained_layout=True) |
| 67 | + .subplots(1,2,sharex=True,sharey=True)) |
| 68 | +errs= [ |
| 69 | + (axs[0],"constant error",0.05), |
| 70 | + (axs[1],"variable error",0.05*np.sin(2*t)**2+0.04), |
| 71 | +] |
| 72 | +fori, (ax,title,err)inenumerate(errs): |
| 73 | +ax.set(title=title,aspect=1,xticks=[],yticks=[]) |
| 74 | +ax.plot(x,y,"k") |
| 75 | +draw_error_band(ax,x,y,err=err, |
| 76 | +facecolor=f"C{i}",edgecolor="none",alpha=.3) |
| 77 | + |
70 | 78 | plt.show() |
71 | 79 |
|
72 | 80 | ############################################################################# |
|