def scatterplot(self):
        """
            Method to draw a scatterplot of the average time to download links
            against time. Add a regression line to show the trend over time.
        """
        try:
            from matplotlib.backends.backend_agg import FigureCanvasAgg as FigureCanvas
            self.FigureCanvas = FigureCanvas
            from matplotlib.figure import Figure
            self.Figure = Figure
            import numpy
        except ImportError:
            return
        try:
            import xlrd
        except:
            import_error += "ERROR: the xlrd modules is needed to record timings\n"
        rec_time_filename = self.config.record_timings_filename
        try:
            workbook = xlrd.open_workbook(filename=rec_time_filename,
                                          formatting_info=True)
        except:
            return
        import numpy
        # Only include the mean in the regression values if there are at least 10 URL timings
        summary = self.read_timings_sheet(workbook)
        (date_summary, gv_mean, gv_std, m, b) = self.report_timings_summary(summary, mean_threshold=10)
        if len(gv_mean) <= 2:
            return
        fig = Figure(figsize=(5, 2.5))
        canvas = self.FigureCanvas(fig)
        ax = fig.add_subplot(111)
        linear = numpy.poly1d([m,b])
        denom = 50/numpy.max(gv_std)
        size = gv_std/denom
        ax.scatter(date_summary, gv_mean, marker="d", s=size)
        ax.plot(date_summary, linear(date_summary), '--r')

        chart = StringIO()
        canvas.print_figure(chart)
        image = chart.getvalue()
        import base64
        base64Img = base64.b64encode(image)
        image = "<img src=\"data:image/png;base64,%s\">" % base64Img
        self.reporter("Scatterplot of average link times per successful run")
        self.reporter(image)
        self.reporter("The trend line has a current slope of %s" % m)
        self.reporter("The y-intercept is %s seconds" % b)
dataset/ETHPy150Open sahana/eden/modules/tests/smoke/broken_links.py/BrokenLinkTest.scatterplot/swapped operands of `/`