importmatplotlib.pyplotaspltimportnumpyasnpfrommatplotlib.projectionsimportPolarAxesfrommatplotlib.transformsimportAffine2Dfrommpl_toolkits.axisartistimportAxes,HostAxes,angle_helperfrommpl_toolkits.axisartist.grid_helper_curvelinearimportGridHelperCurveLineardefcurvelinear_test1(fig):"""    Grid for custom transform.    """deftr(x,y):returnx,y-xdefinv_tr(x,y):returnx,y+xgrid_helper=GridHelperCurveLinear((tr,inv_tr))ax1=fig.add_subplot(1,2,1,axes_class=Axes,grid_helper=grid_helper)# ax1 will have ticks and gridlines defined by the given transform (+# transData of the Axes).  Note that the transform of the Axes itself# (i.e., transData) is not affected by the given transform.xx,yy=tr(np.array([3,6]),np.array([5,10]))ax1.plot(xx,yy)ax1.set_aspect(1)ax1.set_xlim(0,10)ax1.set_ylim(0,10)ax1.axis["t"]=ax1.new_floating_axis(0,3)ax1.axis["t2"]=ax1.new_floating_axis(1,7)ax1.grid(True,zorder=0)defcurvelinear_test2(fig):"""    Polar projection, but in a rectangular box.    """# PolarAxes.PolarTransform takes radian. However, we want our coordinate# system in degreetr=Affine2D().scale(np.pi/180,1)+PolarAxes.PolarTransform()# Polar projection, which involves cycle, and also has limits in# its coordinates, needs a special method to find the extremes# (min, max of the coordinate within the view).extreme_finder=angle_helper.ExtremeFinderCycle(nx=20,ny=20,# Number of sampling points in each direction.lon_cycle=360,lat_cycle=None,lon_minmax=None,lat_minmax=(0,np.inf),)# Find grid values appropriate for the coordinate (degree, minute, second).grid_locator1=angle_helper.LocatorDMS(12)# Use an appropriate formatter.  Note that the acceptable Locator and# Formatter classes are a bit different than that of Matplotlib, which# cannot directly be used here (this may be possible in the future).tick_formatter1=angle_helper.FormatterDMS()grid_helper=GridHelperCurveLinear(tr,extreme_finder=extreme_finder,grid_locator1=grid_locator1,tick_formatter1=tick_formatter1)ax1=fig.add_subplot(1,2,2,axes_class=HostAxes,grid_helper=grid_helper)# make ticklabels of right and top axis visible.ax1.axis["right"].major_ticklabels.set_visible(True)ax1.axis["top"].major_ticklabels.set_visible(True)# let right axis shows ticklabels for 1st coordinate (angle)ax1.axis["right"].get_helper().nth_coord_ticks=0# let bottom axis shows ticklabels for 2nd coordinate (radius)ax1.axis["bottom"].get_helper().nth_coord_ticks=1ax1.set_aspect(1)ax1.set_xlim(-5,12)ax1.set_ylim(-5,10)ax1.grid(True,zorder=0)# A parasite Axes with given transformax2=ax1.get_aux_axes(tr)# note that ax2.transData == tr + ax1.transData# Anything you draw in ax2 will match the ticks and grids of ax1.ax2.plot(np.linspace(0,30,51),np.linspace(10,10,51),linewidth=2)ax2.pcolor(np.linspace(0,90,4),np.linspace(0,10,4),np.arange(9).reshape((3,3)))ax2.contour(np.linspace(0,90,4),np.linspace(0,10,4),np.arange(16).reshape((4,4)),colors="k")if__name__=="__main__":fig=plt.figure(figsize=(7,4))curvelinear_test1(fig)curvelinear_test2(fig)plt.show()

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