检测增减趋势

Question

我正在做一个项目，并试图创建一个函数，通过一次只给它一个元素来检测增加或减少的趋势，因为我不能访问开始时的所有值。

应该是这样的：

第一次迭代：

def detect_trend(arr[0], k, r, q):
       return array_upward_trend, array_downward_trend

第二次迭代：

def detect_trend(arr[1], k, r, q):
       return array_upward_trend, array_downward_trend

诸若此类。

k是定义趋势的东西。这意味着，只有当趋势增加/减少了最后的k元素时，才会形成趋势。虽然如果趋势已经开始形成，并且在q元素之后，我们给函数赋值arr[i]，但是如果这个值是重复的，或者是小范围内的元素，而不是提供给函数的前一个元素r，那么它不会中断趋势的创建。

例如，我有这样的数组

arr=[72 92 42 130 131 412 412 512 345 301 257 101 101 65 72 87 89 80 76 76 75 72 73]

len(arr)迭代后的输出为

array_upward_trend=[[42 130 131 412 412 512],[65 72 87 89]]
array_downward_trend=[[512 345 301 257 101 101 65], [89 80 76 76 75 72 73]]

示例的k=4、q=3和r=0.015 (在本例中r表示1.5%的范围)

我一直没能让这个工作再一次从头开始。我真的很感谢任何形式的帮助

谢谢

Answer 1

首先，欢迎来到stackoverflow。其次，下一次你可能想用不同的方式来问这个问题，因为这个任务有很多子任务。这意味着其他在这里寻求帮助的人可能会跳过这篇文章，从而使回答它变得更不值得。因此，我建议您将复杂的任务拆分成较小的任务。

下面的代码应该可以工作，但效率还不是很高，但可能会给你一个启发。

# =============================================================================
# complete function
# =============================================================================

def detect_trend(arr, number_new, k, r, q):

    # append new element to arr
    arr.append(number_new)

    # up trend
    arr_trends = []
    arr_add = []
    for i, number in enumerate(arr):
        if i != 0:
            previous_number = arr[i-1]

            if len(arr_add) >= q:
                if previous_number/number <= 1+r :
                    bool_logic = True
                else:
                    bool_logic = (previous_number <= number)
            else:
                bool_logic = (previous_number <= number)

            if bool_logic:
                if arr_add == []:
                    arr_add = arr_add + [previous_number]
                arr_add = arr_add + [number]
                if i == len(arr) - 1:
                    arr_trends.append(arr_add)
            else:
                arr_trends.append(arr_add)
                arr_add = []

    array_upward_trend = [trend for trend in arr_trends if len(trend)>=k]


    # down trend
    arr_trends = []
    arr_add = []
    for i, number in enumerate(arr):
        if i != 0:
            previous_number = arr[i-1]

            if len(arr_add) >= q:
                if previous_number/number >= 1-r :
                    bool_logic = True
                else:
                    bool_logic = (previous_number >= number)
            else:
                bool_logic = (previous_number >= number)

            if bool_logic:
                if arr_add == []:
                    arr_add = arr_add + [previous_number]
                arr_add = arr_add + [number]
                if i == len(arr) - 1:
                    arr_trends.append(arr_add)
            else:
                arr_trends.append(arr_add)
                arr_add = []

    array_downward_trend = [trend for trend in arr_trends if len(trend)>=k]

    return arr, array_upward_trend, array_downward_trend

arr = [72,92,42,130,131,412,412,512,345,301,257,101,101,65,72,87,89,80,76,76,75,72,73]
number_new = 74
q = 3
k = 4
r = 0.015

arr, array_upward_trend, array_downward_trend = detect_trend(arr, number_new, k, r, q)

怎么去那里？首先，你可能想把复杂的问题分成一系列简单的问题。然后你开始一个接一个地解决它们，然后再把它们组合起来。以下是我的方法：

首先选择可能最困难的任务，因为如果你失败了，其他任务就无关紧要了。这里是一般的趋势检测。

# =============================================================================
# detect (up) trends
# =============================================================================

arr_trends = []
arr_add = []
for i, number in enumerate(arr):
    if i != 0:
        previous_number = arr[i-1]
        if (previous_number <= number):
            if arr_add == []:
                arr_add = arr_add + [previous_number]
            arr_add = arr_add + [number]
            if i == len(arr) - 1:
                arr_trends.append(arr_add)
        else:
            arr_trends.append(arr_add)
            arr_add = []

# =============================================================================
# consider q and r
# =============================================================================

arr_trends = []
arr_add = []
for i, number in enumerate(arr):
    if i != 0:
        previous_number = arr[i-1]

        if len(arr_add) >= q:
            if previous_number/number <= 1+r :
                bool_logic = True
            else:
                bool_logic = (previous_number <= number)
        else:
            bool_logic = (previous_number <= number)

        if bool_logic:
            if arr_add == []:
                arr_add = arr_add + [previous_number]
            arr_add = arr_add + [number]
            if i == len(arr) - 1:
                arr_trends.append(arr_add)
        else:
            arr_trends.append(arr_add)
            arr_add = []

# =============================================================================
# invert trend logic
# =============================================================================

arr_trends = []
arr_add = []
for i, number in enumerate(arr):
    if i != 0:
        previous_number = arr[i-1]

        if len(arr_add) >= q:
            if previous_number/number >= 1-r :
                bool_logic = True
            else:
                bool_logic = (previous_number >= number)
        else:
            bool_logic = (previous_number >= number)

        if bool_logic:
            if arr_add == []:
                arr_add = arr_add + [previous_number]
            arr_add = arr_add + [number]
            if i == len(arr) - 1:
                arr_trends.append(arr_add)
        else:
            arr_trends.append(arr_add)
            arr_add = []

# =============================================================================
# consider k
# =============================================================================

[trend for trend in arr_trends if len(trend)>=k]

# =============================================================================
# append new element to arr
# =============================================================================

arr.append(number_new)