Question

我从位移传感器捕获了一个数据，一次迭代的delta值如下所示。 0,1,2,4,7,9,14,24,14,10,9,7,3 2,1,0,0,0,0，-1，-3，-5，-7， - 9，-14，-24，-14，-9，-8，-6，-4，-3，-1,0,0,0（其他迭代也有相同的模式。）

我对曲线的最大值和最小值感兴趣。我从一个初始位置开始，然后返回到这个位置以获得一个线的循环（我将取值的部分和来得到总位移或线）。部分和看起来像这样[0,1,3,7,14,23,37,61,75,85,94,101,104,106,107,107,107,107,107,106,103,98 ，91,82,68,44,30,21,13,7,3,0，-1，-1，-1，-1]。我对107和-1（下一个曲线最小值）感兴趣

但我不知道说n的代码。曲线（迭代）。你能帮我解决这个问题吗？

Answer 1

您可以使用此功能获得绝对极值：

def extrema(value, deltas):
    max_value = min_value = value
    for delta in deltas:
        value += delta
        if value < min_value:
            min_value = value
        elif value > max_value:
            max_value = value
    return min_value, max_value

在这里，我已经调整了函数以产生局部极值：

def extrema(value, deltas):
    values = [value]
    for delta in deltas:
        value += delta
        values.append(value)
    average = sum(values)/len(values)
    threshold = (max(values) - min(values))/6
    min_threshold = average - threshold
    max_threshold = average + threshold
    min_value = max_value = None
    for value in values:
        if value < min_threshold:
            if min_value is None or value < min_value:
                min_value = value
        elif value > max_threshold:
            if max_value is None or value > max_value:
                max_value = value
        elif min_value is not None and max_value is not None:
            yield min_value, max_value
            max_value = min_value = None

您可以从此处微调功能。例如，函数可以跳过第一个值直到min_threshold < value < max_threshold找到一个循环的开始，并且如果它没有以一个完整的循环结束它可以产生最后一个极值。

最后，这是一个与示例数据中的点元组一起使用的函数。

class Point(object):

    __slots__ = ('x', 'y')

    def __init__(self, x=0, y=0):
        self.x = x
        self.y = y

    def __repr__(self):
        return str((self.x, self.y))

    def __iadd__(self, other):
        self.x += other.x
        self.y += other.y
        return self

    def __isub__(self, other):
        self.x -= other.x
        self.y -= other.y
        return self

    def __idiv__(self, number):
        self.x /= number
        self.y /= number
        return self

    def abs(self):
        return abs(self.x) + abs(self.y)

    def copy(self):
        return Point(self.x, self.y)


def extrema(moves, jitter=0.1, threshold=1000, sample=16):
    point = Point()
    minpoint = Point()
    maxpoint = Point()
    average = Point()
    average /= 1.0
    turned = False
    for move in moves:
        point += move
        x = point.x
        if x < minpoint.x:
            minpoint.x = x
        elif x > maxpoint.x:
            maxpoint.x = x
        y = point.y
        if y < minpoint.y:
            minpoint.y = y
        elif y > maxpoint.y:
            maxpoint.y = y
        delta = move.copy()
        delta -= average
        delta /= sample
        average += delta
        if average.abs() < jitter:
            if point.abs() > threshold:
                turned = True
            elif turned:
                yield minpoint, maxpoint
                point = Point() # reset (calibrate)
                minpoint = Point()
                maxpoint = Point()
                turned = False


# read data from file
moves = [Point(*map(int, move.split(',')))
    for move in open('data.txt').read().split(';') if move]

# generate extrema
print list(extrema(moves))

Python中曲线的Maxima和Minima点

1 个答案: