Python 迭代行以获得最小值

这是我的数据框：

Date         cell         tumor_size(mm)
25/10/2015    113           51
22/10/2015    222           50
22/10/2015    883           45
20/10/2015    334           35
19/10/2015    564           47
19/10/2015    123           56  
22/10/2014    345           36
13/12/2013    456           44

我想做的是比较不同日子检测到的肿瘤大小。让我们以单元格222为例；我想将其大小与前几天检测到的不同单元格进行比较，例如，我不会将其大小与883单元格进行比较，因为它们是在同一天检测到的。或者我不会将其与113号单元格进行比较，因为它是稍后检测到的。 由于我的数据集太大，所以我对行进行了迭代。如果我用非蟒蛇的方式来解释：

for the cell 222:
     get_size_distance(absolute value):
          (50 - 35 = 15), (50 - 47 = 3), (50 - 56 = 6), (50 - 36 = 14), (44 - 36 = 8)
     get_minumum = 3, I got this value when I compared it with 564, so I will name it as a pait for the cell 222
Then do it for the cell 883

结果输出应如下所示：

   Date         cell         tumor_size(mm)   pair    size_difference
    25/10/2015    113           51            222        1
    22/10/2015    222           50            123        6
    22/10/2015    883           45            456        1
    20/10/2015    334           35            345        1
    19/10/2015    564           47            456        3
    19/10/2015    123           56            456        12
    22/10/2014    345           36            456        8
    13/12/2013    456           44            NaN        NaN 

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我真的很感激你的帮助

这并不漂亮，但我相信它能奏效

a = pd.read_clipboard()
# Cut off last row since it was a faulty date. You can skip this.
df = a.copy().iloc[:-1]

# Convert to dates and order just in case (not really needed I guess).
df['Date'] = df.Date.apply(lambda x: datetime.strptime(x, '%d/%m/%Y'))
df.sort_values('Date', ascending=False)
# Rename column
df = df.rename(columns={"tumor_size(mm)": 'tumor_size'})

# These will be our lists of pairs and size differences.
pairs = []
diffs = []

# Loop over all unique dates
for date in df.Date.unique():
    # Only take dates earlier then current date.
    compare_df = df.loc[df.Date < date].copy()
    # Loop over each cell for this date and find the minimum
    for row in df.loc[df.Date == date].itertuples():
        # If no cells earlier are available use nans.
        if compare_df.empty:
            pairs.append(float('nan'))
            diffs.append(float('nan'))
        # Take lowest absolute value and fill in otherwise
        else:
            compare_df['size_diff'] = abs(compare_df.tumor_size - row.tumor_size)
            row_of_interest = compare_df.loc[compare_df.size_diff == compare_df.size_diff.min()]
            pairs.append(row_of_interest.cell.values[0])
            diffs.append(row_of_interest.size_diff.values[0])

df['pair'] = pairs
df['size_difference'] = diffs

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我不完全明白你在做什么。我知道你只想比较早期的肿瘤。但我不知道你是如何比较它们的，也不知道你是如何选择它们的。我是根据最小距离来选择它们的。例如，最小距离等于6，在222和123单元之间，222单元不应该与564单元配对吗？是的，非常抱歉，谢谢你的澄清。我会试着想一想：）非常感谢你的回答，让我试试：）很乐意帮忙：）

Date    cell    tumor_size  pair    size_difference
0   2015-10-25  113 51  222.0   1.0
1   2015-10-22  222 50  564.0   3.0
2   2015-10-22  883 45  564.0   2.0
3   2015-10-20  334 35  345.0   1.0
4   2015-10-19  564 47  345.0   11.0
5   2015-10-19  123 56  345.0   20.0
6   2014-10-22  345 36  NaN NaN