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Combine two or more columns in a dataframe into a new column with a new name
...t for example is like: A - B instead of A-B. Is it possible to remove this extra space?
– Chetan Arvind Patil
Oct 6 '17 at 2:35
9
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Difference between fold and reduce?
...or they are there to accommodate people with different backgrounds? (E.g.: String and string in C#)
4 Answers
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Get current batchfile directory
...n used above, ending backslash or not) you will need to enclose the entire string in double quotes if path has spaces (i.e. "%batdir%ExtraDir"). You can always use PUSHD %~dp0. [https: // ss64.com/ nt/ syntax-args .html] has more on (%~) parameters.
Note that using (::) at beginning of a line makes...
How do I horizontally center an absolute positioned element inside a 100% width div? [duplicate]
...ent. Now magic happens when margin is set to auto. margin takes up all the extra space(equally on each side) leaving the content to its specified width. This results in content becoming center aligned.
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Read an Excel file directly from a R script
...d to look at your numbers" ... what is the issue with "-" fields? does na.strings="-" address the problem? How many of these issues are generic and how many of them (e.g. numeric fields with commas) can be addressed with other tools such as XLConnect ...?
– Ben Bolker
...
reformat in vim for a nice column layout
...lumn(1) command.
:%!column -t
The above will parse on delimiters inside string literals which is wrong, so you will likely need pre-processing steps and specifying the delimiter for this file for example:
%!sed 's/","/\&/' | column -t -s '&'
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SQL - many-to-many table primary key
... index, on (col1, col2) also handles the 'both' case). The downside is the extra storage needed for the extra column. This is usually not significant, so the advice is far from awful. Nevertheless, if col1 and col2 are big or of very different sizes, you can save yourself some space without hurting ...
Difference between pre-increment and post-increment in a loop?
...value.
++a is known as prefix.
add 1 to a, returns the new value.
C#:
string[] items = {"a","b","c","d"};
int i = 0;
foreach (string item in items)
{
Console.WriteLine(++i);
}
Console.WriteLine("");
i = 0;
foreach (string item in items)
{
Console.WriteLine(i++);
}
Output:
1
2
3
4
0...
C++ Erase vector element by value rather than by position? [duplicate]
...ude <iostream>
#include <range/v3/all.hpp>
int main(int argc, char const *argv[])
{
std::vector<int> vi{2,4,6,8,10};
for (auto& i : vi) {
std::cout << i << std::endl;
}
std::cout << "-----" << std::endl;
std::vector<int>...
Rails: how do I validate that something is a boolean?
...
This does not work, as any string eg, "foo" will be converted into true.
– Ka Mok
Jun 4 '18 at 22:55
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