Excel chart

import numpy as np
from openpyxl.chart import ScatterChart, Reference, Series
from openpyxl.chart.axis import DateAxis
import pandas as pd


def generate_chart_proyeccion(writer_sheet, col_to_graph, start_row, end_row, title):
    """
    Construct a new chart object

    :param writer_sheet: Worksheet were is data located
    :param col_to_graph: Column of data to be plotted
    :param start_row: Row where data starts
    :param end_row: Row where data ends
    :param title: Chart title
    :return: returns a chart object
    """
    chart = ScatterChart()
    chart.title = title
    # chart.x_axis = DateAxis(crossAx=100)
    chart.x_axis.number_format = 'd-mmm HH:MM'
    chart.x_axis.majorTimeUnit = "days"
    chart.x_axis.title = "Fecha"
    chart.y_axis.title = "Valor"
    chart.legend.position = "b"
    chart.width = 5
    data = Reference(writer_sheet, min_col=col_to_graph, max_col=col_to_graph, min_row=start_row, max_row=end_row)
    data_dates = Reference(writer_sheet, min_col=1, max_col=1, min_row=start_row, max_row=end_row) # Corresponde a la columna con la fecha
    serie = Series(data, data_dates, title_from_data=True)
    chart.series.append(serie)
    return chart

# Escribo datos en excel
writer = pd.ExcelWriter("archivo.xlsx", engine='openpyxl')
df = pd.DataFrame(np.random.randn(1000,1), columns=['Dato'], index=pd.date_range('20130101',periods=1000,freq='T'))
df.to_excel(writer, sheet_name="Sheet1", startrow=start_row)
start_row = 1 # En que fila empezar a escribir en excel
end_row = start_row + len(df)
chart = generate_chart_proyeccion(writer.sheets["Sheet1"], 2, start_row, end_row, "A title")
# Añado gráfico a excel
writer.sheets["Sheet1"].add_chart(chart, "C2")
writer.save()