[英]Pandas: How to get all values for a column, where another column's value is a specific value
I have a dataframe which contains a sample_id and mutation: Each sample contains several mutations 我有一个包含sample_id和突变的数据框:每个样品都包含几个突变
sample_id mutation
sample1 mutation_A
sample1 mutation_B
sample1 mutation_D
sample2 mutation_C
sample2 mutation_D
sample3 mutation_A
sample3 mutation_B
sample3 mutation_C
I want to be able to obtain the values where say, mutation_C exists. 我希望能够获得说存在mutation_C的值。 However I want to get all the results out for that sample - 但是,我想获取该样本的所有结果-
df.loc[(df[mutation] == 'mutation_C')]
returns: 收益:
sample_id mutation
sample2 mutation_C
How do I get the rest of sample2 mutation data, so: 我如何获取其余的sample2突变数据,所以:
sample_id mutation
sample2 mutation_C
sample2 mutation_D
I have been trying to use grouopby but can't figure out how to obtain all the results 我一直在尝试使用grouopby,但无法弄清楚如何获得所有结果
First filter all samples
and then filter again by isin
: 首先过滤所有samples
,然后通过isin
再次过滤:
a = df.loc[df['mutation'] == 'mutation_C', 'sample_id']
df = df[df['sample_id'].isin(a)]
print (a)
3 sample2
7 sample3
Name: sample_id, dtype: object
df = df[df['sample_id'].isin(a)]
print (df)
sample_id mutation
3 sample2 mutation_C
4 sample2 mutation_D
5 sample3 mutation_A
6 sample3 mutation_B
7 sample3 mutation_C
Assuming you have other data, a neater idea would be to set the index the way you are after. 假设您还有其他数据,那么一个更整洁的想法是按照您的方式设置索引。 (I've added a dummy column with df['value'] = 1
) (我添加了一个df['value'] = 1
的虚拟列)
>>> a = df.set_index(['mutation', 'sample_id'])
>>> a.sort_index()
value
mutation sample_id
mutation_A sample1 1
sample3 1
mutation_B sample1 1
sample3 1
mutation_C sample2 1
sample3 1
mutation_D sample1 1
sample2 1
>>> a.loc['mutation_C']
value
sample_id
sample2 1
sample3 1
If you really need the sample_ids as a list then you could do: 如果您确实需要sample_ids作为列表,则可以执行以下操作:
>>> a.loc['mutation_C'].index.tolist()
['sample2', 'sample3']
Not what you asked but perhaps another useful view: 不是您问的,而是另一个有用的观点:
>>> df.pivot_table(values='value', index='sample_id', columns='mutation')
mutation mutation_A mutation_B mutation_C mutation_D
sample_id
sample1 1.0 1.0 NaN 1.0
sample2 NaN NaN 1.0 1.0
sample3 1.0 1.0 1.0 NaN
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