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Aggregate / summarize multiple variables per group (e.g. sum, mean)
...[, lapply(.SD, sum), by=.(year, month), .SDcols=c("x1","x2")]
setDF(df2) # convert back to dataframe
Using the plyr package
require(plyr)
df2 <- ddply(df1, c("year", "month"), function(x) colSums(x[c("x1", "x2")]))
Using summarize() from the Hmisc package
(column headings are messy in my ex...
Java - escape string to prevent SQL injection
...e the "replaceAll" string function. Ultimately I need a function that will convert any existing \ to \\ , any " to \" , any ' to \' , and any \n to \\n so that when the string is evaluated by MySQL SQL injections will be blocked.
...
Sending multipart/formdata with jQuery.ajax
...ust leave the processData flag set to false, otherwise, jQuery will try to convert your FormData into a string, which will fail.
You may now retrieve the file in PHP using:
$_FILES['file-0']
(There is only one file, file-0, unless you specified the multiple attribute on your file input, in which...
What does -1 mean in numpy reshape?
A numpy matrix can be reshaped into a vector using reshape function with parameter -1. But I don't know what -1 means here.
...
Java logical operator short-circuiting
...he behaviour in a simple example:
public boolean longerThan(String input, int length) {
return input != null && input.length() > length;
}
public boolean longerThan(String input, int length) {
return input != null & input.length() > length;
}
The 2nd version uses the no...
What is the use of the pipe symbol in YAML?
...dicates that multi-line "folded" scalar follows, meaning that newlines are converted to spaces. For example:
>>> import yaml
>>> yaml.load("""
... |
... This is a multi-line
... literal style scalar.
... """)
'This is a multi-line\nliteral style scalar.\n'
>>> yaml.loa...
How to change href of tag on button click through javascript
...
no href makes it an anchor, click converts to a link, pretty normal
– Free Consulting
Dec 6 '10 at 12:07
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Omitting one Setter/Getter in Lombok
...r, like this:
@Getter(AccessLevel.NONE)
@Setter(AccessLevel.NONE)
private int mySecret;
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Worth switching to zsh for casual use? [closed]
...s not clear that zmv is just renaming files; I thought you might have been converting the format. I don't know what "hashes" support even means. This post seems like it's only "useful" to people that already know zsh.
– mpen
Mar 26 '14 at 17:52
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How do I get the parent directory in Python?
...directory so you can put it in a JSON string. It would be kind of silly to convert to a Pathlib object and back again for that.
If none of the above apply, use Pathlib.
What is Pathlib?
If you don't know what Pathlib is, the Pathlib module is a terrific module that makes working with files e...