Python中曲线的最大值和最小值点

Question

我从位移传感器捕获了一个数据，一次迭代的增量值看起来像这样。0、1、2、4、7、9、14日,24日,14日,10日,9日,7日,3 2 1 0,0,0,0,1,3,5,7,9,-14年,-24年,-14年,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点很感兴趣。我从一个初始位置开始，然后回到这个位置进行循环(我已经取了这些值的部分和来获得总位移或直线)。部分和是这样的[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

但我不知道代码说n不。曲线(迭代)。你能帮我一下吗?

Answer 1

您可以使用这个函数来获取绝对极值:

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

这里我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

您可以从这里对函数进行微调。例如，该函数可以跳过第一个值直到min_threshold < value < max_threshold以找到循环的开始，并且在结束时，如果它没有以完整的循环结束，它可以产生最后一个极值。

最后，这里有一个函数，可以像您的示例数据一样处理点元组。

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))