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Convert data.frame column format from character to factor
... the format (class) of some columns of my data.frame object ( mydf ) from charactor to factor .
6 Answers
...
Why is it slower to iterate over a small string than a small list?
...string took longer than doing the same operation on a list of small single character strings. Any explanation? It's almost 1.35 times as much time.
...
Boost.Asio的简单使用(Timer,Thread,Io_service类) - C/C++ - 清泛网 - 专注C/C++及内核技术
...I标准发送数据。)
using boost::asio::ip::tcp;
int main(int argc, char* argv[])
{
try
{
if (argc != 2)
{
std::cerr << "Usage: client <host>" << std::endl;
return 1;
}
用asio进行网络连接至少需要一个boost::asi...
COUNT DISTINCT with CONDITIONS
...bination of Tag & Entry ID when [Entry Id]>0
select count(distinct(concat(tag,entryId)))
from customers
where id>0
In the output it will display the count of unique values
Hope this helps
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How can I get a JavaScript stack trace when I throw an exception?
...trace() {
function st2(f) {
return !f ? [] :
st2(f.caller).concat([f.toString().split('(')[0].substring(9) + '(' + f.arguments.join(',') + ')']);
}
return st2(arguments.callee.caller);
}
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How can I get a file's size in C++? [duplicate]
...
#include <fstream>
std::ifstream::pos_type filesize(const char* filename)
{
std::ifstream in(filename, std::ifstream::ate | std::ifstream::binary);
return in.tellg();
}
See http://www.cplusplus.com/doc/tutorial/files/ for more information on files in C++.
edit: this answ...
Replace all non Alpha Numeric characters, New Lines, and multiple White Space with one Space
.../[\W_]+/g," ");
\W is the negation of shorthand \w for [A-Za-z0-9_] word characters (including the underscore)
Example at regex101.com
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follo...
What is the default initialization of an array in Java?
...t is a 0.
For float/double that is a 0.0
For booleans that is a false.
For char that is the null character '\u0000' (whose decimal equivalent is 0).
When you create an array of something, all entries are also zeroed. So your array contains five zeros right after it is created by new.
Note (based...
Format number to 2 decimal places
...ect ifnull(format(100.00, 1, 'en_US'), 0)
100.0
Show as Percentage
Select concat(ifnull(format(100.00, 0, 'en_US'), 0), '%')
100%
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How do I remove the first characters of a specific column in a table?
In SQL, how can I remove the first 4 characters of values of a specific column in a table? Column name is Student Code and an example value is ABCD123Stu1231 .
I want to remove first 4 chars from my table for all records
...