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Drop data frame columns by name
...to keep and refer to them by name :
keeps <- c("y", "a")
DF[keeps]
EDIT :
For those still not acquainted with the drop argument of the indexing function, if you want to keep one column as a data frame, you do:
keeps <- "y"
DF[ , keeps, drop = FALSE]
drop=TRUE (or not mentioning it) will ...
How to upgrade PostgreSQL from version 9.6 to version 10.1 without losing data?
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launchctl unload ~/Library/LaunchAgents/homebrew.mxcl.postgresql.plist
Initialize a new 10.1 database:
initdb /usr/local/var/postgres10.1 -E utf8
run pg_upgrade (note: change bin version if you're upgrading from something other than below):
pg_upgrade -v \
-d /usr/local/var/postgres \
-D...
Getting rid of bullet points from
...ssuming that didn't work, you might want to combine the id-based selector with the li in order to apply the css to the li elements:
#otis li {
list-style-type: none;
}
Reference:
list-style-type at the Mozilla Developer Center.
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What's the point of having pointers in Go?
...that pointers in Go allow mutation of a function's arguments, but wouldn't it have been simpler if they adopted just references (with appropriate const or mutable qualifiers). Now we have pointers and for some built-in types like maps and channels implicit pass by reference.
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mongoDB/mongoose: unique if not null
...the desired behavior of ensuring unique values but allowing multiple docs without the field by setting the sparse option to true when defining the index. As in:
email : {type: String, trim: true, index: true, unique: true, sparse: true}
Or in the shell:
db.users.ensureIndex({email: 1}, {unique:...
Most efficient way to make the first character of a String lower case?
...n 1.
Results
Benchmark Mode Cnt Score Error Units
MyBenchmark.test1 thrpt 20 10463220.493 ± 288805.068 ops/s
MyBenchmark.test2 thrpt 20 14730158.709 ± 530444.444 ops/s
MyBenchmark.test3 thrpt 20 16079551.751 ± 56884.357 ops/s
MyBenchmark.test4 thrpt ...
At runtime, find all classes in a Java application that extend a base class
...follow
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edited Nov 5 '18 at 18:39
answered Feb 11 '12 at 14:29
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Input with display:block is not a block, why not?
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Check out what I came up with, a solution using the relatively unknown box-sizing:border-box style from CSS 3. This allows a 'true' 100% width on any element regardless of that elements' padding and/or borders.
<!DOCTYPE html PUBLIC "-//W3C//DTD ...
spring scoped proxy bean
...one explain the usage of the spring @ScopedProxy annotation? I thought it had something to do with session scoped beans, but I'm not quite sure what.
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Changing all files' extensions in a folder with one command on Windows
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You can use ren (as in rename):
ren *.XXX *.YYY
And of course, switch XXX and YYY for the appropriate extensions. It will change from XXX to YYY. If you want to change all extensions, just use the wildcard again:
ren *.* *.YYY
One way to make this work recursively is with the FOR comman...