Method get_streamline_arrows

plotly/figure_factory/_streamline.py:319–394

Makes an arrow for each streamline. Gets angle of streamline at 1/3 mark and creates arrow coordinates based off of user defined angle and arrow_scale. :param (array) st_x: x-values for all streamlines :param (array) st_y: y-values for all streamlines

(self)

            self.st_y[index].append(np.nan)

    def get_streamline_arrows(self):
        """
        Makes an arrow for each streamline.

        Gets angle of streamline at 1/3 mark and creates arrow coordinates
        based off of user defined angle and arrow_scale.

        :param (array) st_x: x-values for all streamlines
        :param (array) st_y: y-values for all streamlines
        :param (angle in radians) angle: angle of arrowhead. Default = pi/9
        :param (float in [0,1]) arrow_scale: value to scale length of arrowhead
            Default = .09
        :rtype (list, list) arrows_x: x-values to create arrowhead and
            arrows_y: y-values to create arrowhead
        """
        arrow_end_x = np.empty((len(self.st_x)))
        arrow_end_y = np.empty((len(self.st_y)))
        arrow_start_x = np.empty((len(self.st_x)))
        arrow_start_y = np.empty((len(self.st_y)))
        for index in range(len(self.st_x)):
            arrow_end_x[index] = self.st_x[index][int(len(self.st_x[index]) / 3)]
            arrow_start_x[index] = self.st_x[index][
                (int(len(self.st_x[index]) / 3)) - 1
            ]
            arrow_end_y[index] = self.st_y[index][int(len(self.st_y[index]) / 3)]
            arrow_start_y[index] = self.st_y[index][
                (int(len(self.st_y[index]) / 3)) - 1
            ]

        dif_x = arrow_end_x - arrow_start_x
        dif_y = arrow_end_y - arrow_start_y

        orig_err = np.geterr()
        np.seterr(divide="ignore", invalid="ignore")
        streamline_ang = np.arctan(dif_y / dif_x)
        np.seterr(**orig_err)

        ang1 = streamline_ang + (self.angle)
        ang2 = streamline_ang - (self.angle)

        seg1_x = np.cos(ang1) * self.arrow_scale
        seg1_y = np.sin(ang1) * self.arrow_scale
        seg2_x = np.cos(ang2) * self.arrow_scale
        seg2_y = np.sin(ang2) * self.arrow_scale

        point1_x = np.empty((len(dif_x)))
        point1_y = np.empty((len(dif_y)))
        point2_x = np.empty((len(dif_x)))
        point2_y = np.empty((len(dif_y)))

        for index in range(len(dif_x)):
            if dif_x[index] >= 0:
                point1_x[index] = arrow_end_x[index] - seg1_x[index]
                point1_y[index] = arrow_end_y[index] - seg1_y[index]
                point2_x[index] = arrow_end_x[index] - seg2_x[index]
                point2_y[index] = arrow_end_y[index] - seg2_y[index]
            else:
                point1_x[index] = arrow_end_x[index] + seg1_x[index]