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Does the ternary operator exist in R?
... TRUE TRUE TRUE TRUE
[49] TRUE TRUE
> ifelse(cars$speed > 20, 'fast', 'slow')
[1] "slow" "slow" "slow" "slow" "slow" "slow" "slow" "slow" "slow" "slow"
[11] "slow" "slow" "slow" "slow" "slow" "slow" "slow" "slow" "slow" "slow"
[21] "slow" "slow" "slow" "slow" "slow" "slow" "slow" "slow"...
Fast way to discover the row count of a table in PostgreSQL
...unt FROM myschema.mytable;
You get a close estimate like this (extremely fast):
SELECT reltuples::bigint AS estimate FROM pg_class where relname='mytable';
How close the estimate is depends on whether you run ANALYZE enough. It is usually very close.
See the PostgreSQL Wiki FAQ.
Or the dedicate...
Fast way of counting non-zero bits in positive integer
I need a fast way to count the number of bits in an integer in python.
My current solution is
9 Answers
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Fast ceiling of an integer division in C / C++
...der in its result so this really needs only one division and would be very fast
– phuclv
Jan 25 '14 at 11:15
This is t...
Is git-svn dcommit after merging in git dangerous?
...xplicitly creating a merge commit (a commit with two parents) instead of a fast-forward. To ensure all commits in the svn-tracking branch are single-parent commits, all merges must either be fast-forwards (--ff-only can help with this) or, if trunk has changed behind your back, a --squash, right?
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rejected master -> master (non-fast-forward)
...low is broken. Features should be developed in branches and merged without fast-forwarding and if a feature has "failed" you should revert the merge commit (preferably do your testing in an integration branch first before you merge a feature to master). No idea about Eclipse though.
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Why is Go so slow (compared to Java)?
...e not particularly optimising, so the code they produce isn't particularly fast.
They're designed to run fast themselves and produce code that's OK (there is a bit of optimisation). gccgo uses GCC's existing optimisation passes, and might provide a more pointful comparison with C, but gccgo isn't f...
Define: What is a HashSet?
...t implementations of Sets. Some make insertion and lookup operations super fast by hashing elements. However, that means that the order in which the elements were added is lost. Other implementations preserve the added order at the cost of slower running times.
The HashSet class in C# goes for the...
Fast check for NaN in NumPy
I'm looking for the fastest way to check for the occurrence of NaN ( np.nan ) in a NumPy array X . np.isnan(X) is out of the question, since it builds a boolean array of shape X.shape , which is potentially gigantic.
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Augmented Reality SDK with OpenCV [closed]
...o find tutorials on the topic, which steps to follow, possible algorithms, fast and efficient coding for real-time performance etc.
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