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Speed up the loop operation in R
...Biggest problem and root of ineffectiveness is indexing data.frame, I mean all this lines where you use temp[,].
Try to avoid this as much as possible. I took your function, change indexing and here version_A
dayloop2_A <- function(temp){
res <- numeric(nrow(temp))
for (i in 1:nrow(te...
Selecting multiple columns in a pandas dataframe
...).
df1 = df[['a', 'b']]
Alternatively, if it matters to index them numerically and not by their name (say your code should automatically do this without knowing the names of the first two columns) then you can do this instead:
df1 = df.iloc[:, 0:2] # Remember that Python does not slice inclusive of...
Algorithm to find Largest prime factor of a number
...
Actually there are several more efficient ways to find factors of big numbers (for smaller ones trial division works reasonably well).
One method which is very fast if the input number has two factors very close to its square r...
Deleting lines from one file which are in another file
... speed of Jona Christopher Sahnwal's answer.
– Alex Hall
Nov 8 '15 at 21:15
1
@arnaud576875: Are ...
Select distinct values from a table field
...ant any ordering to be applied to a query, not even the default ordering, call order_by() with no parameters.
and distinct() in the note where it discusses issues with using distinct() with ordering.
To query your DB, you just have to call:
models.Shop.objects.order_by().values('city').distinct(...
How do you trigger a block after a delay, like -performSelector:withObject:afterDelay:?
Is there a way to call a block with a primitive parameter after a delay, like using performSelector:withObject:afterDelay: but with an argument like int / double / float ?
...
Ruby send vs __send__
I understand the concept of some_instance.send but I'm trying to figure out why you can call this both ways. The Ruby Koans imply that there is some reason beyond providing lots of different ways to do the same thing. Here are the two examples of usage:
...
Group by in LINQ
...
Absolutely - you basically want:
var results = from p in persons
group p.car by p.PersonId into g
select new { PersonId = g.Key, Cars = g.ToList() };
Or as a non-query expression:
var results = persons.GroupBy(
...
Ruby on Rails: Delete multiple hash keys
...re unaware of the Hash#except method ActiveSupport adds to Hash.
It would allow your code to be simplified to:
redirect_to my_path(params.except(:controller, :action, :other_key))
Also, you wouldn't have to monkey patch, since the Rails team did it for you!
...
Find the PID of a process that uses a port on Windows
...t on Windows (e.g. port: "9999")
netstat -aon | find "9999"
-a Displays all connections and listening ports.
-o Displays the owning process ID associated with each connection.
-n Displays addresses and port numbers in numerical form.
Output:
TCP 0.0.0.0:9999 0.0.0.0:0 LISTENING...