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Remove columns from dataframe where ALL values are NA
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160
Try this:
df <- df[,colSums(is.na(df))<nrow(df)]
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How to sign an android apk file
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smac89
22.6k1010 gold badges7272 silver badges106106 bronze badges
answered Jan 31 '11 at 16:02
NanneNanne
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How can I scan barcodes on iOS?
...ial C++ port of the core library. The port is a little old, from circa the 0.9 release of the Java code, but should still work reasonably well.
If you need to scan other formats, like 1D formats, you could continue the port of the Java code within this project to C++.
EDIT: Barcodes and the iphone...
Java ArrayList how to add elements at the beginning
... beginning of the array (so it has the lowest index) and if the array has 10 elements adding a new results in deleting the oldest element (the one with the highest index).
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Determine if a function exists in bash
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answered Sep 17 '08 at 18:00
JBBJBB
3,85733 gold badges2222 silver badges2525 bronze badges
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Tool to read and display Java .class versions
...s.java"
public class MyClass
SourceFile: "MyClass.java"
minor version: 0
major version: 46
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To only show the version:
WINDOWS> javap -verbose MyClass | find "version"
LINUX > javap -verbose MyClass | grep version
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How to use int.TryParse with nullable int? [duplicate]
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answered Aug 2 '10 at 18:44
Jon SkeetJon Skeet
1211k772772 gold badges85588558 silver badges88218821 bronze badges
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Difference between Dictionary and Hashtable [duplicate]
...ing (and compile-time verification)
use without boxing
If you are .NET 2.0 or above, you should prefer Dictionary<TKey,TValue> (and the other generic collections)
A subtle but important difference is that Hashtable supports multiple reader threads with a single writer thread, while Dictiona...
Using node.js as a simple web server
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1013
Simplest Node.js server is just:
$ npm install http-server -g
Now you can run a server via ...
PHP 5.4 Call-time pass-by-reference - Easy fix available?
...lone are enough to correctly pass the argument by reference. As of PHP 5.3.0, you will get a warning saying that "call-time pass-by-reference" is deprecated when you use & in foo(&$a);.
For example, instead of using:
// Wrong way!
myFunc(&$arg); # Deprecated pass-by-refe...