我有一个DataFrame
Close Delta
Date
2020-05-11 2920.50 -440
2020-05-11 2920.25 -9
2020-05-11 2920.25 -27
2020-05-11 2920.50 2
2020-05-11 2920.75 117
现在我正在使用此功能计算“关闭”的连续增量:
tickbox = []
cumtickCount = 0
for i in range(len(df.index)):
if df.Close[i] > df.Close[i-1]:
cumtickCount += 1
tickbox.append(cumtickCount)
else:
cumtickCount = 0
我得到了列表,但在这里我也不明白为什么值以1开头而不是0
复选框:
[1,
1,
2,
3,
1,
2,
3,
4,
5,
6,
1,
1,
2,
3,
4,
5,
6,
7,
8,
9,
1,
2,
3,
4,
5,
如果我将列表转换为df列
ct = pd.Series(tickbox)
df['consec_tick'] = ct
我得到NaN值
Close Delta consec_tick
Date
2020-05-11 2920.50 -440 NaN
2020-05-11 2920.25 -9 NaN
2020-05-11 2920.25 -27 NaN
2020-05-11 2920.50 2 NaN
2020-05-11 2920.75 117 NaN
如果我这样分配列表:
df.assign(new_col=consec_tickup)
或
df['consec_tick'] = consec_tickup
我收到以下错误:
---------------------------------------------------------------------------
ValueError Traceback (most recent call last)
<ipython-input-57-9d3e9ad7ceb3> in <module>
7 cumtickCount += 1
8 #tickbox.append(cumtickCount)
----> 9 df['consec_tick'] = tickbox
10 else:
11 cumtickCount = 0
/opt/anaconda3/lib/python3.7/site-packages/pandas/core/frame.py in __setitem__(self, key, value)
3470 else:
3471 # set column
-> 3472 self._set_item(key, value)
3473
3474 def _setitem_slice(self, key, value):
/opt/anaconda3/lib/python3.7/site-packages/pandas/core/frame.py in _set_item(self, key, value)
3547
3548 self._ensure_valid_index(value)
-> 3549 value = self._sanitize_column(key, value)
3550 NDFrame._set_item(self, key, value)
3551
/opt/anaconda3/lib/python3.7/site-packages/pandas/core/frame.py in _sanitize_column(self, key, value, broadcast)
3732
3733 # turn me into an ndarray
-> 3734 value = sanitize_index(value, self.index, copy=False)
3735 if not isinstance(value, (np.ndarray, Index)):
3736 if isinstance(value, list) and len(value) > 0:
/opt/anaconda3/lib/python3.7/site-packages/pandas/core/internals/construction.py in sanitize_index(data, index, copy)
610
611 if len(data) != len(index):
--> 612 raise ValueError("Length of values does not match length of index")
613
614 if isinstance(data, ABCIndexClass) and not copy:
ValueError: Length of values does not match length of index
如何正确地将'tickbox'中的值分配给该列?
答案 0 :(得分:1)
您的解决方案存在一些问题,可能是由于我对目标的误解。
如果您希望该列具有与另一列相同数量的值,则需要为每个元素的tickbox
添加一个值。就您而言,您没有在else
分支中添加任何内容,这意味着您实际上是在跳过某些值。
另一个问题是,第一个值可能需要设置为0
。相反,当i = 0
时,您正在将元素0
与元素-1
进行比较。尝试输入代码时,我实际上得到了KeyError: -1
。
考虑到以上问题,我们可以重写该函数:
def consecutive_ticks(close_prices):
# start with 0 for the first data point
ticks = [0]
count = 0
# go from element 1 to the last element
for i in range(1, len(close_prices)):
if close_prices[i] > close_prices[i-1]:
count += 1
else:
count = 0
# we append the current count anyway.
# it's either going to be an increment, or it's 0 if "close" is smaller
ticks.append(count)
return ticks
这将返回与close_prices
系列相同长度的列表。因此,您可以通过以下方式简单地将其添加到数据框中:
df['consec_tick'] = consecutive_ticks(df.Close)