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Is there a better way to dynamically build an SQL WHERE clause than by using 1=1 at its beginning?
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Save the conditions in a list:
List<string> conditions = new List<string>();
if ...
Pandas: drop a level from a multi-level column index?
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321
You can use MultiIndex.droplevel:
>>> cols = pd.MultiIndex.from_tuples([("a", "b"), ("...
Print all but the first three columns
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19 Answers
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How to print last two columns using awk
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194
You can make use of variable NF which is set to the total number of fields in the input recor...
How to sort a list/tuple of lists/tuples by the element at a given index?
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10 Answers
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Generate random number between two numbers in JavaScript
Is there a way to generate a random number in a specified range (e.g. from 1 to 6: 1, 2, 3, 4, 5, or 6) in JavaScript?
23 A...
Find indices of elements equal to zero in a NumPy array
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numpy.where() is my favorite.
>>> x = numpy.array([1,0,2,0,3,0,4,5,6,7,8])
>>> numpy.where(x == 0)[0]
array([1, 3, 5])
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What is Weak Head Normal Form?
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These expressions are all in normal form:
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(2, "hello")
\x -> (x + 1)
These expressions are not in normal form:
1 + 2 -- we could evaluate this to 3
(\x -> x + 1) 2 -- we could apply the function
"he" ++ "llo" -- we could apply the (++)
(1 + 1, 2 + 2) ...
How do I find a “gap” in running counter with SQL?
...gap" in a counter column in an SQL table. For example, if there are values 1,2,4 and 5 I'd like to find out 3.
20 Answers
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Can dplyr package be used for conditional mutating?
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Use ifelse
df %>%
mutate(g = ifelse(a == 2 | a == 5 | a == 7 | (a == 1 & b == 4), 2,
ifelse(a == 0 | a == 1 | a == 4 | a == 3 | c == 4, 3, NA)))
Added - if_else: Note that in dplyr 0.5 there is an if_else function defined so an alternative would be to replace ifelse with i...