Plot a scalar value.
        :param value: int or float, the value on the y-axis
        :param step: int or float, the value on the x-axis
        :param name: String, the name of the variable to be used during visualization

def scalar(self, value, step, name):
        """
        Plot a scalar value.
        :param value: int or float, the value on the y-axis
        :param step: int or float, the value on the x-axis
        :param name: String, the name of the variable to be used during visualization
        """
        # Spaces not allowed for scalar variable name
        assert len(name.split(" ")) < 2, "Ensure that you don't have spaces in your variable name, use '_' instead."
        name = "scalar_" + name
        self.previous.append(name)
        if self.previous[-1] not in self.previous[:-1]:
            self.c.execute("""INSERT INTO {time_stamp_table} (
                              variable_name, variable_type
                              ) VALUES ('{variable}', '{type}')"""
                           .format(time_stamp_table=self.time_stamp, variable=name, type="scalar"))
        else:
            self.previous.pop()

        self.c.execute("""CREATE TABLE IF NOT EXISTS {variable_table_name} (
                          X_value FLOAT, Y_value FLOAT, time VARCHAR
                          )""".format(variable_table_name=self.time_stamp + '_' + name))

        self.c.execute("""INSERT INTO {variable_table_name} (
                          X_value, Y_value, time) VALUES ('{x}', '{y}', '{time}'
                          )""".format(variable_table_name=self.time_stamp + '_' + name,
                                      x=step, y=value, time=datetime.datetime.now()))
        self.conn.commit()