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Want to find records with no associated records in Rails
... get everyone with no friends in the first case:
Person.where('id NOT IN (SELECT DISTINCT(person_id) FROM friends)')
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Drop data frame columns by name
...op=FALSE to keep R from converting your data frame to a vector if you only select a single column. Don't forget that data frames are lists, so list selection (one-dimensional like I did) works perfectly well and always returns a list. Or a data frame in this case, which is why I prefer to use it.
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How to create a listbox in HTML without allowing multiple selection?
...eate a simple listbox, but one of the requirements is to DISALLOW multiple selection. Most of the code for listboxes goes like this -
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Select first 4 rows of a data.frame in R
How can I select the first 4 rows of a data.frame :
5 Answers
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Selecting with complex criteria from pandas.DataFrame
...se pandas it has some built in functions for comparison. So if you want to select values of "A" that are met by the conditions of "B" and "C" (assuming you want back a DataFrame pandas object)
df[['A']][df.B.gt(50) & df.C.ne(900)]
df[['A']] will give you back column A in DataFrame format.
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Correct way to add external jars (lib/*.jar) to an IntelliJ IDEA project
...ps for adding external jars in IntelliJ IDEA:
Click File from the toolbar
Select Project Structure option (CTRL + SHIFT + ALT + S on Windows/Linux, ⌘ + ; on Mac OS X)
Select Modules at the left panel
Select Dependencies tab
Select + icon
Select 1 JARs or directories option
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How can I configure NetBeans to insert tabs instead of a bunch of spaces?
...it Tab for indenting code, I like to get a real tab. Meaning that when I select that, I only have one large thing selected. NetBeans inserts 5 spaces instead of a tab when I hit Tab . Is there a way I can change that?
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How to integrate CSS pre-processing within Eclipse? [closed]
...and then click OK.
Find the *.scss entry in the File Associations list and select it.
After selecting *.scss, on the bottom pane Associated editors:, click the Add... button.
Make sure Internal editors is selected on the top, then find and select CSS Editor and then click OK.
This associated the f...
MySQL: Transactions vs Locking Tables
...ransactions vs locking tables to ensure database integrity and make sure a SELECT and UPDATE remain in sync and no other connection interferes with it. I need to:
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Select unique or distinct values from a list in UNIX shell script
I have a ksh script that returns a long list of values, newline separated, and I want to see only the unique/distinct values. It is possible to do this?
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