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Dynamically select data frame columns using $ and a character value
...the second is a data.frame
mtcars[[var]]
mtcars[var]
You can perform the ordering without loops, using do.call to construct the call to order. Here is a reproducible example below:
# set seed for reproducibility
set.seed(123)
df <- data.frame( col1 = sample(5,10,repl=T) , col2 = sample(5,10,r...
What are sessions? How do they work?
...
Because HTTP is stateless, in order to associate a request to any other request, you need a way to store user data between HTTP requests.
Cookies or URL parameters ( for ex. like http://example.com/myPage?asd=lol&boo=no ) are both suitable ways to ...
Python group by
...8544'], 'type': 'NOT'}]
Note both of these do not respect the original order of the keys. You need an OrderedDict if you need to keep the order.
>>> from collections import OrderedDict
>>> res = OrderedDict()
>>> for v, k in input:
... if k in res: res[k].append(v)
...
How can I echo a newline in a batch file?
... is expected. The best summary I know of is at dostips.com/forum/viewtopic.php?p=4554#p4554. It kind of leaves you hanging, but no one has ever come up with a scenario where ECHO( fails.
– dbenham
Apr 18 '14 at 17:20
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How to make button look like a link?
...t for the sake of simplicity i will use them here):
<a href="some/page.php" title="perform some js action" onclick="callFunction(this.href);return false;">watch and learn</a>
with this.href you can even access the target of the link in your function. return false will just prevent bro...
How to use SQL Order By statement to sort results case insensitive?
I have a SQLite database that I am trying to sort by Alphabetical order. The problem is, SQLite doesn't seem to consider A=a during sorting, thus I get results like this:
...
What optimizations can GHC be expected to perform reliably?
... also explains the passes fairly well. This page explains the optimization ordering, though, like the majority of the Trac Wiki, it is out of date.
For specifics, the best thing to do is probably to look at how a specific program is compiled. The best way to see which optimizations are being perfor...
Warning the user/local/mysql/data directory is not owned by the mysql user
...restart.
Reference: https://coolestguidesontheplanet.com/get-apache-mysql-php-phpmyadmin-working-osx-10-10-yosemite/
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List all base classes in a hierarchy of given class?
...s NewClass.mro(): a list of the class and all its ancestor classes, in the order used for method resolution.
>>> class A(object):
>>> pass
>>>
>>> class B(A):
>>> pass
>>>
>>> import inspect
>>> inspect.getmro(B)
(<c...
90后创业四年:曾经觉得不公 后来愿赌服输 - 资讯 - 清泛网 - 专注C/C++及内核技术
...自己踩过这个坑，回顾我第一次创业时遇到的合伙人内讧问题，背后其实反映的是创始人的心态——创业很轻松，玩一玩就能创业。我甚至会建议一些人别大学一毕业就创业，因为心态不摆正，一定会失败。创业是神圣的行为，...