Python 从熊猫数据帧整体返回最大值，而不是基于列或行
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return max value from panda dataframe as a whole, not based on column or rows
提问by Boosted_d16
I am trying to get the max value from a panda dataframe as whole. I am not interested in what row or column it came from. I am just interested in a single max value within the dataframe.
我试图从整个熊猫数据框中获取最大值。我对它来自哪一行或哪一列不感兴趣。我只对数据框中的单个最大值感兴趣。
Here is my dataframe:
这是我的数据框：
df = pd.DataFrame({'group1': ['a','a','a','b','b','b','c','c','d','d','d','d','d'],
'group2': ['c','c','d','d','d','e','f','f','e','d','d','d','e'],
'value1': [1.1,2,3,4,5,6,7,8,9,1,2,3,4],
'value2': [7.1,8,9,10,11,12,43,12,34,5,6,2,3]})
This is what it looks like:
这是它的样子：
group1 group2 value1 value2
0 a c 1.1 7.1
1 a c 2.0 8.0
2 a d 3.0 9.0
3 b d 4.0 10.0
4 b d 5.0 11.0
5 b e 6.0 12.0
6 c f 7.0 43.0
7 c f 8.0 12.0
8 d e 9.0 34.0
9 d d 1.0 5.0
10 d d 2.0 6.0
11 d d 3.0 2.0
12 d e 4.0 3.0
Expected output:
预期输出：
43.0
I was under the assumption that df.max() would do this job but it returns a max value for each column but I am not interested in that. I need the max from an entire dataframe.
我假设 df.max() 会完成这项工作，但它为每列返回一个最大值，但我对此不感兴趣。我需要整个数据帧的最大值。
采纳答案by unutbu
The max of all the values in the DataFrame can be obtained using df.to_numpy().max(), or for pandas < 0.24.0we use df.values.max():
可以使用 获得 DataFrame 中所有值的最大值df.to_numpy().max()，或者pandas < 0.24.0我们使用df.values.max()：
In [10]: df.to_numpy().max()
Out[10]: 'f'
The max is frather than 43.0 since, in CPython2,
最大值f不是 43.0，因为在 CPython2 中，
In [11]: 'f' > 43.0
Out[11]: True
In CPython2, Objects of different types ... are
ordered by their type names. So any strcompares as greater than any intsince 'str' > 'int'.
在 CPython2 中，不同类型的对象......按它们的类型名称排序。所以 anystr比 any 更大，int因为'str' > 'int'.
In Python3, comparison of strings and ints raises a TypeError.
在 Python3 中，字符串和整数的比较会产生一个TypeError.
To find the max value in the numeric columns only, use
要仅在数字列中查找最大值，请使用
df.select_dtypes(include=[np.number]).max()
回答by ntg
For the max, check the previous answer... For the max of the values use e.g.:
对于最大值，请检查上一个答案...对于值的最大值，请使用例如：
val_cols = [c for c in df.columns if c.startswith('val')]
print df[val_cols].max()
回答by aileronajay
Max can be found in these two steps:
Max可以在这两个步骤中找到：
maxForRow = allData.max(axis=0) #max for each row
globalMax = maxForRow.max(); #max across all rows
回答by Rilwan Adewoyin
Hi the simplest answer is the following. Answer:
您好，最简单的答案如下。回答：
df.max().max()
Explanation: series = df.max()give you a Series containing the maximum values for each column.
Therefore series.max()gives you the maximum for the whole dataframe.
说明：series = df.max()给你一个包含每列最大值的系列。
因此，series.max()为您提供整个数据帧的最大值。
:) best answers are usually the simplest
:) 最好的答案通常是最简单的
