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Convert data.frame column format from character to factor
...yr::mutate_if() to convert all character columns or dplyr::mutate_at() for select named character columns to factors:
library(dplyr)
# all character columns to factor:
df <- mutate_if(df, is.character, as.factor)
# select character columns 'char1', 'char2', etc. to factor:
df <- mutate_at(d...
Why use the params keyword?
...
You could also use return args.Select(x => x + 2).Sum();
– bbvg
Aug 22 '17 at 21:07
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How to add an auto-incrementing primary key to an existing table, in PostgreSQL?
...t have to have a placeholder for it in the Insert statement. Then a simple select * into the target table auto populated this column. Here are the two SQL statements that I used on PostgreSQL 9.6.4.
ALTER TABLE target ADD COLUMN some_column SERIAL;
INSERT INTO target SELECT * from source;
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Android: Getting a file URI from a content URI?
In my app the user is to select an audio file which the app then handles. The problem is that in order for the app to do what I want it to do with the audio files, I need the URI to be in file format. When I use Android's native music player to browse for the audio file in the app, the URI is a cont...
How do I use WebStorm for Chrome Extension Development?
...ript > Libraries
Click Download
Make sure TypeScript community stubs is selected
Select chrome from the list (you can find it quickly by just typing chrome)
Click Download and Install
Click OK to close the Settings dialog.
Steps 2-6 illustrated below:
In Subsequent Projects
In any subse...
How to access remote server with local phpMyAdmin client?
... and now your phpMyAdmin home page will change and it will show a field to select the server.
Now you can select you server and access your remote database by entering username and password for that database.
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Can't execute jar- file: “no main manifest attribute”
...o specify the Application's entry point in eclipse.
When you say Export,
Select Jar and next
[ give it a name in the next window ] and next
and next again
and you'll see " Select the class of the application entry point".
Just pick a class and Eclipse will automatically build a cool MANIFEST....
Difference between id and name attributes in HTML
...mitted, there is just the one value in the response - the radio button you selected.
Of course, there's more to it than that, but it will definitely get you thinking in the right direction.
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How can I create a unique constraint on my column (SQL Server 2008 R2)?
...the "General" tab.
Make sure you have the column you want to make unique selected in the "columns" box.
Change the "Type" box to "Unique Key".
Click "Close".
You see a little asterisk in the file window, this means changes are not yet saved.
Press Save or hit Ctrl+s. It should save, and your colu...
Are database triggers evil? [closed]
...lumns wouldn't exist and you'd have to process a function on each row when selecting them. That's likely to kill DBMS performance, far better to create the auto-generated column at insert/update time since that's the only time it changes.
Also, lack of triggers would prevent data rules from being e...