Python 熊猫比较下一行
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Pandas compare next row
提问by NinjaGaiden
I have a dataframe like this
我有一个这样的数据框
d={}
d['z']=['Q8','Q8','Q7','Q9','Q9']
d['t']=['10:30','10:31','10:38','10:40','10:41']
d['qty']=[20,20,9,12,12]
I want compare first row with second row
我想比较第一行和第二行
- is qty same as next row AND
- is t greater in the next row AND
- is z value same as next row
- 与下一行数量相同 AND
- 在下一行中 t 更大 AND
- z 值是否与下一行相同
The desired value is
所需的值是
qty t z valid
0 20 2015-06-05 10:30:00 Q8 False
1 20 2015-06-05 10:31:00 Q8 True
2 9 2015-06-05 10:38:00 Q7 False
3 12 2015-06-05 10:40:00 Q9 False
4 12 2015-06-05 10:41:00 Q9 True
采纳答案by firelynx
Looks like you want to use the Series.shiftmethod.
看起来您想使用该Series.shift方法。
Using this method, you can generate new columns which are offset to the original columns. Like this:
使用此方法，您可以生成与原始列偏移的新列。像这样：
df['qty_s'] = df['qty'].shift(-1)
df['t_s'] = df['t'].shift(-1)
df['z_s'] = df['z'].shift(-1)
Now you can compare these:
现在你可以比较这些：
df['is_something'] = (df['qty'] == df['qty_s']) & (df['t'] < df['t_s']) & (df['z'] == df['z_s'])
Here is a simplified example of how Series.shiftworks to compare next row to the current:
以下是Series.shift将下一行与当前行进行比较的工作原理的简化示例：
df = pd.DataFrame({"temp_celcius":pd.np.random.choice(10, 10) + 20}, index=pd.date_range("2015-05-15", "2015-05-24"))
df
temp_celcius
2015-05-15 21
2015-05-16 28
2015-05-17 27
2015-05-18 21
2015-05-19 25
2015-05-20 28
2015-05-21 25
2015-05-22 22
2015-05-23 29
2015-05-24 25
df["temp_c_yesterday"] = df["temp_celcius"].shift(1)
df
temp_celcius temp_c_yesterday
2015-05-15 21 NaN
2015-05-16 28 21
2015-05-17 27 28
2015-05-18 21 27
2015-05-19 25 21
2015-05-20 28 25
2015-05-21 25 28
2015-05-22 22 25
2015-05-23 29 22
2015-05-24 25 29
df["warmer_than_yesterday"] = df["temp_celcius"] > df["temp_c_yesterday"]
temp_celcius temp_c_yesterday warmer_than_yesterday
2015-05-15 21 NaN False
2015-05-16 28 21 True
2015-05-17 27 28 False
2015-05-18 21 27 False
2015-05-19 25 21 True
2015-05-20 28 25 True
2015-05-21 25 28 False
2015-05-22 22 25 False
2015-05-23 29 22 True
2015-05-24 25 29 False
If I misunderstood your query, please post a comment and I'll update my answer.
如果我误解了您的查询，请发表评论，我会更新我的答案。
