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dplyr summarise: Equivalent of “.drop=FALSE” to keep groups with zero length in output
...ime, especially since your data are already factored, you can use complete from "tidyr" to get what you might be looking for:
library(tidyr)
df %>%
group_by(b) %>%
summarise(count_a=length(a)) %>%
complete(b)
# Source: local data frame [3 x 2]
#
# b count_a
# (fctr) (int)...
How can I concatenate two arrays in Java?
...
I found a one-line solution from the good old Apache Commons Lang library. ArrayUtils.addAll(T[], T...)
Code:
String[] both = ArrayUtils.addAll(first, second);
share
...
Kotlin secondary constructor
...
Instead of extending first constructor directly from the second one can delegate to another secondary constructor, that already does it:
– Picrochole
Jun 6 '17 at 6:20
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REST URI convention - Singular or plural name of resource while creating it
...t.". Ah the famous line I hear so often and get sick and tired of hearing from people. Conventions matter and SHOULD be debated constructively amongst the community, that's where better solutions come about and good practices. When you are using both plural and singular for resource names in URIs...
How to convert lazy sequence to non-lazy in Clojure
... depends on what type of non lazy sequence you want to get:
Take your pick from:
an ex-lazy (fully evaluated) lazy sequence (doall ... )
a list for sequential access (apply list (my-lazy-seq)) OR (into () ...)
a vector for later random access (vec (my-lazy-seq))
a map or a set if you h...
Is it possible to figure out the parameter type and return type of a lambda?
.../trunk/include/tacklelib/… As a solution for broken links: try to search from the root, Luke.
– Andry
Jan 17 '19 at 7:59
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What does “O(1) access time” mean?
...gardless of their size, and linked lists, which must be traversed in order from the beginning to access a given item.
The other operation usually discussed is insert. A collection can be O(1) for access but O(n) for insert. In fact an array has exactly this behavior, because to insert an item in ...
How to convert an ArrayList containing Integers to primitive int array?
...i -> i).toArray();
What it does is:
getting a Stream<Integer> from the list
obtaining an IntStream by mapping each element to itself (identity function), unboxing the int value hold by each Integer object (done automatically since Java 5)
getting the array of int by calling toArray
Yo...
How to drop a database with Mongoose?
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There is no method for dropping a collection from mongoose, the best you can do is remove the content of one :
Model.remove({}, function(err) {
console.log('collection removed')
});
But there is a way to access the mongodb native javascript driver, which can be ...
What's the best way to get the current URL in Spring MVC?
...UriComponentsBuilder and its static methods:
ServletUriComponentsBuilder.fromCurrentContextPath()
ServletUriComponentsBuilder.fromCurrentServletMapping()
ServletUriComponentsBuilder.fromCurrentRequestUri()
ServletUriComponentsBuilder.fromCurrentRequest()
They use RequestContextHolder under the h...