大约有 44,000 项符合查询结果（耗时：0.0287秒） [XML]
Apply a function to every row of a matrix or a data frame
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182
You simply use the apply() function:
R> M <- matrix(1:6, nrow=3, byrow=TRUE)
R> M
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What is the most efficient/elegant way to parse a flat table into a tree?
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14 Answers
14
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Replace all 0 values to NA
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Replacing all zeroes to NA:
df[df == 0] <- NA
Explanation
1. It is not NULL what you should want to replace zeroes with. As it says in ?'NULL',
NULL represents the null object in R
which is unique and, I guess, can be seen as the most uninformative and empty object.1 Then it b...
Calculate difference in keys contained in two Python dictionaries
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21 Answers
21
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Pandas index column title or name
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In [8]: df.index.name = 'foo'
In [9]: df.index.name
Out[9]: 'foo'
In [10]: df
Out[10]:
Column 1
foo
Apples 1
Oranges 2
Puppies 3
Ducks 4
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Type-juggling and (strict) greater/lesser-than comparisons in PHP
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edited May 23 '17 at 11:47
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answered Apr 4 '13 at 14:10
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Regex to validate date format dd/mm/yyyy
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I modified it to take dd/mm/yyyy, dd-mm-yyyy or dd.mm.yyyy.
^(?:(?:31(\/|-|\.)(?:0?[13578]|1[02]))\1|(?:(?:29|30)(\/|-|\.)(?:0?[13-9]|1[0-2])\2))(?:(?:1[6-9]|[2-9]\d)?\d{2})$|^(?:29(\/|-|\.)0?2\3(?:(?:(?:1[6-9]|[2-9]\d)?(?:0[48]|[2468][048]|[13579][26])|(?:(?:16|[2468][048]|[3579][26])00))))$...
How can I use “:” as an AWK field separator?
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"-F" is a command line argument, not AWK syntax. Try:
echo "1: " | awk -F ":" '/1/ {print $1}'
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