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Numbering rows within groups in a data frame
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Use ave, ddply, dplyr or data.table:
df$num <- ave(df$val, df$cat, FUN = seq_along)
or:
library(plyr)
ddply(df, .(cat), mutate, id = seq_along(val))
or:
library(dplyr)
df %>% group_by(cat) %>% mutate(id = row_number())
or (the most memory efficient, as it assigns by reference w...
How do I fix certificate errors when running wget on an HTTPS URL in Cygwin?
...his not insecure to install root certificate authorities from a random web site, especially with haxx in the name?
– Chloe
Jun 29 '12 at 2:04
6
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How to use PyCharm to debug Scrapy projects
...l IcecatCrawler can also be executed like this: python /Library/Python/2.7/site-packages/scrapy/cmdline.py crawl IcecatCrawler
Try to find the scrapy.cmdline package.
In my case the location was here: /Library/Python/2.7/site-packages/scrapy/cmdline.py
Create a run/debug configuration inside PyCha...
Changing website favicon dynamically
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Google can give you a site's favicon by using this url, replacing stackoverflow.com with the domain you want: s2.googleusercontent.com/s2/favicons?domain=stackoverflow.com
– kirb
Oct 3 '11 at 4:20
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What is href=“#” and why is it used?
On many websites I see links that have href="#" . What does it mean? What is it used for?
9 Answers
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Place cursor at the end of text in EditText
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There is a function called append for ediitext which appends the string value to current edittext value and places the cursor at the end of the value.
You can have the string value as the current ediitext value itself and call append();...
Section vs Article HTML5
...n
a tabbed dialog box, or the numbered sections of a thesis. A Web
site's home page could be split into sections for an introduction,
news items, and contact information.
Note: Authors are encouraged to use the article element instead of the
section element when it would make s...
Finding all objects that have a given property inside a collection [duplicate]
...st for the Matchers. Some will argue that this is not Java-style, but it's fun how this guy twisted Java to make a bit of functional programming. Have a look at the source code also, it's quite sci-fi.
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How do I get the base URL with PHP?
...ERVER predefined variable.
If you plan on using https, you can use this:
function url(){
return sprintf(
"%s://%s%s",
isset($_SERVER['HTTPS']) && $_SERVER['HTTPS'] != 'off' ? 'https' : 'http',
$_SERVER['SERVER_NAME'],
$_SERVER['REQUEST_URI']
);
}
echo url();
#=> htt...
How to upgrade Eclipse for Java EE Developers?
... way to upgrade an Eclipse installation? I have tried browsing the eclipse site but I cannot find an useful description.
3...