utils.py 文件源码

def get_linear_regression(xdata, ydata):
    """ Calculate the coefficients of the linear equation corresponding
    to the linear regression of a series of points. """
    try:
        import numpy
        return tuple(numpy.polyfit(xdata, ydata, 1))
    except ImportError:
        # numpy not available
        # try something approximate and simple
        datasize = len(xdata)
        sum_x = float(sum(xdata))
        sum_y = float(sum(ydata))
        sum_xx = float(sum(map(lambda x: x * x, xdata)))
        sum_products = float(sum([xdata[i] * ydata[i]
                                  for i in range(datasize)]))
        a = (sum_products - sum_x * sum_y / datasize) / (
            sum_xx - (sum_x * sum_x) / datasize)
        b = (sum_y - a * sum_x) / datasize
        return a, b