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How to sum a variable by group
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Using aggregate:
aggregate(x$Frequency, by=list(Category=x$Category), FUN=sum)
Category x
1 First 30
2 Second 5
3 Third 34
In the example above, multiple dimensions can be specified in the list. Multiple aggregated metrics of the same d...
Does Python have “private” variables in classes?
... emulate private variables for some reason, you can always use the __ prefix from PEP 8. Python mangles the names of variables like __foo so that they're not easily visible to code outside the class that contains them (although you can get around it if you're determined enough, just like you can get...
Why does Windows64 use a different calling convention from all other OSes on x86-64?
...D has an ABI specification that describes the calling convention to use on x86-64. All OSes follow it, except for Windows which has it's own x86-64 calling convention. Why?
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In c# is there a method to find the max of 3 numbers?
Like Math.Max but takes 3 or params of int?
10 Answers
10
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C dynamically growing array
...aw" list of in-game entities, and I intend to make an array holding an index number (int) of an indeterminate number of entities, for processing various things. I would like to avoid using too much memory or CPU for keeping such indexes...
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Could not load file or assembly Microsoft.SqlServer.management.sdk.sfc version 11.0.0.0
...S SQL Server 2008 R2 and when I try to update model from database under EDMX file I am facing that error.
12 Answers
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push_back vs emplace_back
...s strictly equivalent to push_back(Type&& _Val).
But the real C++0x form of emplace_back is really useful: void emplace_back(Args&&...);
Instead of taking a value_type it takes a variadic list of arguments, so that means that you can now perfectly forward the arguments and construc...
Python initializing a list of lists [duplicate]
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The problem is that they're all the same exact list in memory. When you use the [x]*n syntax, what you get is a list of n many x objects, but they're all references to the same object. They're not distinct instances, rather, just n references to the same instance.
T...
print memory address of Python variable [duplicate]
...d() returns the 'id' of a variable or object, but this doesn't return the expected 0x3357e182 style I was expecting to see for a memory address.
I want to do something like print &x , where x is a C++ int variable for example.
How can I do this in Python?
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Mac OS X安装Bochs - 更多技术 - 清泛网 - 专注C/C++及内核技术
Mac OS X安装Bochs1.安装x11;2.开启Mac OS X的root用户3.configure我在这里遇到的问题是，提示我少一个这个头文件X11 extensions Xrandr.h谷歌了一下，机子...1.安装x11;
2.开启Mac OS X的root用户
3.configure
我在这里遇到的问题是，提示我少一个...