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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...
Preserving signatures of decorated functions
... """Computes x*y + 2*z"""
return x*y + 2*z
print funny_function("3", 4.0, z="5")
# 22
help(funny_function)
# Help on function funny_function in module __main__:
#
# funny_function(x, y, z=3)
# Computes x*y + 2*z
Python 3.4+
functools.wraps() from stdlib preserves signatures since Py...
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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Splitting String with delimiter
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tim_yatestim_yates
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MySQL foreign key constraints, cascade delete
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answered May 26 '10 at 22:45
Marc BMarc B
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initializing a boolean array in java
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answered Mar 2 '10 at 16:42
BalusCBalusC
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`elif` in list comprehension conditionals
...ere designed exactly for this sort of use-case:
>>> l = [1, 2, 3, 4, 5]
>>> ['yes' if v == 1 else 'no' if v == 2 else 'idle' for v in l]
['yes', 'no', 'idle', 'idle', 'idle']
Hope this helps :-)
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How to not run an example using roxygen2?
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4 Answers
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Appropriate datatype for holding percent values?
...ent (e.g. 100.00% stored as 1.0000), I would store the data in a decimal(5,4) data type with a CHECK constraint that ensures that the values never exceed 1.0000 (assuming that is the cap) and never go below 0 (assuming that is the floor). If you are going to store their face value (e.g. 100.00% is s...
Understanding exactly when a data.table is a reference to (vs a copy of) another data.table
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Yes, it's subassignment in R using <- (or = or ->) that makes a copy of the whole object....