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How to join (merge) data frames (inner, outer, left, right)
...rge on multiple columns by giving by a vector, e.g., by = c("CustomerId", "OrderId").
If the column names to merge on are not the same, you can specify, e.g., by.x = "CustomerId_in_df1", by.y = "CustomerId_in_df2" where CustomerId_in_df1 is the name of the column in the first data frame and Custom...
IntelliJ show JavaDocs tooltip on mouse over
In Eclipse, when hovering over a method, variable, etc. a tooltip is displayed with the corresponding JavaDocs. Is there such a feature in IntelliJ?
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Array vs. Object efficiency in JavaScript
...If you need keys (numbers or strings), use an object. If you just need an (ordered) list, use arrays. Period. Performance doesn't enter the discussion. If performance is crucial and you could live with your keys either way, try which one works better for you.
– deceze♦
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List of zeros in python [duplicate]
... 0 zeroes, zlists[1] is a list of 1 zero, zlists[2] is a list of 2 zeroes, etc.
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Get keys from HashMap in Java
...ray.
The problem, of course, is that a set doesn't promise to keep your order. If you only have one item in your HashMap, you're good, but if you have more than that, it's best to loop over the map, as other answers have done.
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library not found for -lPods
..."Undefined symbols" messages to sort through, due to a missing SQLite lib, etc.
– Hot Licks
Nov 11 '14 at 22:37
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How do I remove  from the beginning of a file?
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Three words for you:
Byte Order Mark (BOM)
That's the representation for the UTF-8 BOM in ISO-8859-1. You have to tell your editor to not use BOMs or use a different editor to strip them out.
To automatize the BOM's removal you can use awk as shown ...
How do I specify the exit code of a console application in .NET?
...ptions above).
Depending on your application (console, service, web app, etc) different methods can be used.
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heroku - how to see all the logs
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Heroku treats logs as time-ordered streams of events. Accessing *.log files on the filesystem is not recommended in such an environment for a variety of reasons.
First, if your app has more than one dyno then each log file only represents a partial vi...
How to access random item in list?
...fle<T>(this IEnumerable<T> source)
{
return source.OrderBy(x => Guid.NewGuid());
}
}
For a strongly typed list, this would allow you to write:
var strings = new List<string>();
var randomString = strings.PickRandom();
If all you have is an ArrayList, you can...