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How does one reorder columns in a data frame?
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You can also use the subset function:
data <- subset(data, select=c(3,2,1))
You should better use the [] operator as in the other answers, but it may be useful to know that you can do a subset and a column reorder operation in a single command.
Update:
You can also use the select...
Update multiple rows in same query using PostgreSQL
...;
-- populate table with dummy rows
insert into results_dummy
(id, status)
select unnest(array[1,2,3,4,5]::int[]) as id, unnest(array['a','b','c','d','e']::text[]) as status;
select * from results_dummy;
-- THE update of multiple rows with/by different values
update results_dummy as rd
set stat...
HTML input file selection event not firing upon selecting the same file
Is there any chance to detect every file selection the user made for an HTML input of type file element?
7 Answers
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What is the difference between Left, Right, Outer and Inner Joins?
...ow you begin your query impacts the outcome of the join type. For example, SELECT * FROM students RIGHT OUTER JOIN lockers... would result in a different outcome than SELECT * FROM lockers RIGHT OUTER JOIN students.... Great answer, but would love to see it updated with complete SQL queries
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Use didSelectRowAtIndexPath or prepareForSegue method for UITableView?
... I'll have to pass a couple objects to the detail view. But do I use didSelectRowAtIndex or -(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender ?
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How to create a drop-down list?
...eated one.
dropdown.setAdapter(adapter);
Notes:
You can use a setOnItemSelectedListener with this.
You can add a strings list from xml
There is an appCompat version of this view.
More information:
This is the basics but there is more to be self taught with experimentation.
https://developer....
Renew Provisioning Profile
...gn).
I discovered that if I change something on the screen (in my case, I selected a previously
unused device), "Submit" darkens (becomes available).
Click on "Submit".
You're quietly (another UI problem :) taken back to the prior page, and the
"Download" and "Edit" buttons are gone, and the status...
LINQ: Distinct values
...d it should be okay:
var query = doc.Elements("whatever")
.Select(element => new {
id = (int) element.Attribute("id"),
category = (int) element.Attribute("cat") })
.Distinct();
If you're trying to get a dis...
Insert text with single quotes in PostgreSQL
...token1$escape ' with ''$token1$ is nested$token2$
Pay attention if the $ character should have special meaning in your client software. You may have to escape it in addition. This is not the case with standard PostgreSQL clients like psql or pgAdmin.
That is all very useful for writing plpgsql fu...
How can I remove the string “\n” from within a Ruby string?
...gsub. The different quote marks behave differently.
Double quotes " allow character expansion and expression interpolation ie. they let you use escaped control chars like \n to represent their true value, in this case, newline, and allow the use of #{expression} so you can weave variables and, well...