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std::next_permutation Implementation Explanation
...td:next_permutation was implemented so I extracted the the gnu libstdc++ 4.7 version and sanitized the identifiers and formatting to produce the following demo...
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For each row return the column name of the largest value
...ample reproducible):
DF <- data.frame(V1=c(2,8,1),V2=c(7,3,5),V3=c(9,6,4))
colnames(DF)[apply(DF,1,which.max)]
[1] "V3" "V1" "V2"
A faster solution than using apply might be max.col:
colnames(DF)[max.col(DF,ties.method="first")]
#[1] "V3" "V1" "V2"
...where ties.method can be any of "rando...
How does numpy.histogram() work?
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edited Feb 4 '12 at 15:31
answered Feb 4 '12 at 15:09
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Select multiple columns in data.table by their numeric indices
... Henrik
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answered Nov 14 '12 at 17:28
Josh O'BrienJosh O'Brien
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Clojure: cons (seq) vs. conj (list)
...ts to insert into a collection, while cons takes just one:
(conj '(1 2 3) 4 5 6)
; => (6 5 4 1 2 3)
(cons 4 5 6 '(1 2 3))
; => IllegalArgumentException due to wrong arity
Another difference is in the class of the return value:
(class (conj '(1 2 3) 4))
; => clojure.lang.PersistentList
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How to select rows with one or more nulls from a pandas DataFrame without listing columns explicitly
I have a dataframe with ~300K rows and ~40 columns.
I want to find out if any rows contain null values - and put these 'null'-rows into a separate dataframe so that I could explore them easily.
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How exactly does tail recursion work?
...lexey Frunze
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How assignment works with Python list slice?
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4 Answers
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Apply a function to every row of a matrix or a data frame
...:6, nrow=3, byrow=TRUE)
R> M
[,1] [,2]
[1,] 1 2
[2,] 3 4
[3,] 5 6
R> apply(M, 1, function(x) 2*x[1]+x[2])
[1] 4 10 16
R>
This takes a matrix and applies a (silly) function to each row. You pass extra arguments to the function as fourth, fifth, ... arguments to app...
NameError: global name 'xrange' is not defined in Python 3
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answered Jun 19 '13 at 13:14
Martijn Pieters♦Martijn Pieters
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