draw_linechart.py

def draw_linechart(Num_Year):
    ''' 
    This is the function to make a plot
    '''
    # since many figures will be generated for animation, old axes need to be cleared before drawing new axes
    ax.clear() 
    ax2.clear()
    
    # select data till the indicated year
    df_tmp=df_sydney.loc[df_sydney['Year'] <= Num_Year] 
    
    # The frame of the whole figure, use the full data
    # excluding from the automatic legend element selection by 
    # defining a label starting with an underscore.
    ax.plot(df_sydney.Year, df_sydney.max_tmp_year*0, label='_1', color='#222222', zorder=1)
    
    # The horizontal line to indicate 40 degree, use the full data
    ax.plot(df_sydney.Year, (df_sydney.max_tmp_year**0)*40, label='_1', color='#fc280f', linestyle='dashed', alpha=0.1, linewidth=0.5, zorder=1)

    # The horizontal line to indicate 20 days, use the full data
    ax2.plot(df_sydney.Year, (df_sydney.hot_day**0)*20, label='_2', color='#eeb72b', linestyle='dashed', alpha=0.1, linewidth=0.5, zorder=1)

    # line plot
    ax.plot(df_tmp.Year, df_tmp.max_tmp_year, label='Yearly max. temp. ($^\circ$C)', 
            color='#fc280f', zorder=3)
    ax2.plot(df_tmp.Year, df_tmp.hot_day, label='Yearly accumulated days above 30$^\circ$C', 
             color='#eeb72b', zorder=3)

    # dot at the end of the line
    ax.scatter(df_tmp.Year.values[-1], df_tmp.max_tmp_year.values[-1], color='#fc280f', s=60, edgecolor ='w', linewidth=1, zorder=4)
    ax2.scatter(df_tmp.Year.values[-1], df_tmp.hot_day.values[-1], color='#eeb72b', s=60, edgecolor ='w', linewidth=1, zorder=4)

    # text associated with the dot in the figure
    ax.text(df_tmp.Year.values[-1], df_tmp.max_tmp_year.values[-1]+5,
            s='Temp. {}'.format(df_tmp.max_tmp_year.values[-1]), size=10, 
            color='#fc280f', ha='center', va='bottom', zorder=5)
    ax2.text(df_tmp.Year.values[-1], df_tmp.hot_day.values[-1]+0.7, 
             s='{} Days'.format(int(df_tmp.hot_day.values[-1])), size=10, 
             color='#eeb72b', ha='center', va='bottom', zorder=5)

    # display year in the background
    ax.text(0.5, 0.5, s=df_tmp.Year.values[-1], fontweight='bold', size=60, 
            color='#e3e3e3', ha='center', va="center", 
            alpha=0.5, transform=ax.transAxes, zorder=2)

    # legend for red line
    l1 = ax.legend(loc='upper left')
    
    for text in l1.get_texts():
        text.set_color('#e3e3e3')
    
    # legend for yellow line
    l2 = ax2.legend(loc='upper right')
    
    for text in l2.get_texts():
        text.set_color('#e3e3e3')
    
    # set the y-axis to have enough space for other elements, such as legends
    ax.set_ylim(0, df_sydney.max_tmp_year.max()*1.68)
    # do not show the grid in the background
    ax.grid(b=None)
    ax.set_ylabel('Temperature ($^\circ$C)', color='#e3e3e3')
    
    ax2.grid(b=None) # Don't show grid of ax2 
    ax2.set_ylim(df_tmp.hot_day.min()-5, df_tmp.hot_day.max()*1.5)
    ax2.set_ylabel('Day', color='#e3e3e3')
    
    # set color for axes frame
    ax2.spines['bottom'].set_color('#e3e3e3')  
    ax2.spines['right'].set_color('#e3e3e3')  
    ax2.spines['left'].set_color('#e3e3e3')  
    ax2.spines['top'].set_color('#e3e3e3') 

    # Retrieve an element of a plot and set properties
    for tick in ax.xaxis.get_ticklabels():
        tick.set_fontsize('x-small')

    ax.margins(x=0.05)

    ax.text(0.00, 1.05, 'Sydney Annual Maximum Temperature From 1859 to 2019', color='#e3e3e3', 
             transform=ax.transAxes, size=17, weight='light', ha='left')
    ax.text(0.00, -0.1, 'Data source from http://www.bom.gov.au', color='#e3e3e3', 
             transform=ax.transAxes, size=5, weight='light', ha='left')