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Extracting specific columns from a data frame
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Using the dplyr package, if your data.frame is called df1:
library(dplyr)
df1 %>%
select(A, B, E)
This can also be written without the %>% pipe as:
select(df1, A, B, E)
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Iterating through a list in reverse order in java
...es the elegance of the for each syntax. +1 anyway.
– Allain Lalonde
Jan 20 '10 at 15:35
26
Callin...
How can I temporarily disable a foreign key constraint in MySQL?
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To turn off foreign key constraint globally, do the following:
SET GLOBAL FOREIGN_KEY_CHECKS=0;
and remember to set it back when you are done
SET GLOBAL FOREIGN_KEY_CHECKS=1;
WARNING: You should only do this when you are doing single user mode maintenance. ...
How to change the ROOT application?
...tdown your Tomcat from the its bin directory (sh shutdown.sh). Then delete all the content of your Tomcat webapps folder (rm -fr *). Then rename your WAR file to ROOT.war, and finally start your Tomcat from the bin directory (sh startup.sh).
Leave your war file in $CATALINA_BASE/webapps under its or...
Auto increment in phpmyadmin
... Had a similar issue and this fixed my problem
– Callat
Sep 4 '17 at 15:44
1
wow, so simple. w...
How to remove leading zeros from alphanumeric text?
...re 0 characters (you could use 0+ as well). The replaceFirst just replaces all those 0 characters at the start with nothing.
And if, like Vadzim, your definition of leading zeros doesn't include turning "0" (or "000" or similar strings) into an empty string (a rational enough expectation), simply p...
How to initialize List object in Java?
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If you check that link, you'll find some classes that implement List:
All Known Implementing Classes:
AbstractList, AbstractSequentialList, ArrayList, AttributeList, CopyOnWriteArrayList, LinkedList, RoleList, RoleUnresolvedList, Stack, Vector
Those can be instantiated. Use their links t...
What is the simplest and most robust way to get the user's current location on Android?
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Here's what I do:
First of all I check what providers are enabled. Some may be disabled on the device, some may be disabled in application manifest.
If any provider is available I start location listeners and timeout timer. It's 20 seconds in my exampl...
Convert String array to ArrayList [duplicate]
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In summary all you need is the line List<String> wordList = Arrays.asList(words); . Is this correct?
– Keale
Aug 5 '14 at 2:40
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Tool for generating railroad diagram used on json.org [closed]
...string and value using string ::= ... and value ::= ... The references are all shown.
Check out some of the example diagrams on the page. They have XML and even EBNF itself.
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