Function to plot chloropleth map from shapefiles

plot_chloropleth.py

import shapefile
import seaborn as sns


sf = shapefile.Reader("voronoi/voronoi.shp")
shapes = sf.shapes()

def getMid(bbox):
    '''
    Helper function to get midpoint of a bounding box
    '''
    x=bbox[0]+((bbox[2]-bbox[0])/2)
    y=bbox[1]+((bbox[3]-bbox[1])/2)
    return (x,y)

def plotCholoropleth(vals,fileName=None,labels=None,title=None):
    '''
    Plots Poygons in global variable shapes and fills
    with @vals. Places in quartile buckets for range 0-1
    '''

    #colours=sns.color_palette(n_colors=nColours)
    colours=sns.color_palette("RdBu",n_colors=4)
    
    assert min(vals)>-0.0001 and max(vals)<1.000001
    
    fig=plt.figure()
    ax=fig.add_subplot(111)

    for nshp in xrange(len(shapes)):
        ptchs   = []
        pts     = np.array(shapes[nshp].points)
        prt     = shapes[nshp].parts
        par     = list(prt) + [pts.shape[0]]
        for pij in xrange(len(prt)):
            ptchs.append(Polygon(pts[par[pij]:par[pij+1]]))
            plt.plot(pts[par[pij:0],par[pij+1:1]])
                    
        if labels:
            (x,y)=getMid(shapes[nshp].bbox)
            
            plt.annotate(s=towers[nshp],xy=(x,y),xycoords='data',size=6)
        
        if vals[nshp]<0.25:
            colour=colours[0]
        elif vals[nshp]<0.5:
            colour=colours[1]
        elif vals[nshp]<0.75:
            colour=colours[2]
        else:
            colour=colours[3]
            
        ax.add_collection(PatchCollection(ptchs,edgecolor='white', linewidths=0.2,color=colour,alpha=1.0))
        
    rangeStrings=['$\phi <$0.25','0.25$<\phi<$0.5','0.5$<\phi<$0.75','0.75$<\phi<$1.0']
        
    for n,c in enumerate(colours):
        plt.annotate(s=rangeStrings[n],xy=(0.1,0.25-(n*0.07)),xycoords='figure fraction',color=c,size=16)
    
    if title:
        plt.title(title,size=18)
    
    plt.axis('off')
    
    ###############################################################################################################################
    ### Inset
    axins = inset_axes(ax,width="30%",height="30%",loc=1)
    
    for nshp in xrange(len(shapes)):
        ptchs   = []
        pts     = np.array(shapes[nshp].points)
        prt     = shapes[nshp].parts
        par     = list(prt) + [pts.shape[0]]
        for pij in xrange(len(prt)):
            ptchs.append(Polygon(pts[par[pij]:par[pij+1]]))
            plt.plot(pts[par[pij:0],par[pij+1:1]])
        
        if vals[nshp]<0.25:
            colour=colours[0]
        elif vals[nshp]<0.5:
            colour=colours[1]
        elif vals[nshp]<0.75:
            colour=colours[2]
        else:
            colour=colours[3]
            
        axins.add_collection(PatchCollection(ptchs,edgecolor='white', linewidths=0.2,color=colour,alpha=1.0))
        
    plt.xlim(-13.3,-13.08)
    plt.ylim(8.32,8.6)
    plt.xticks([],[])
    plt.yticks([],[])
    axins.spines['bottom'].set_color('grey')
    axins.spines['top'].set_color('grey') 
    axins.spines['right'].set_color('grey')
    axins.spines['left'].set_color('grey')
    #plt.tight_layout()
        
    if fileName:
        plt.savefig('images/%s' % fileName,dpi=250)

spinglass_mutability.png