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How does one reorder columns in a data frame?
... has four columns like so df[,c(1,2,3,4)].
Note the first comma means keep all the rows, and the 1,2,3,4 refers to the columns.
To change the order as in the above question do df2[,c(1,3,2,4)]
If you want to output this file as a csv, do write.csv(df2, file="somedf.csv")
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Pandas: Looking up the list of sheets in an excel file
...eet_names attribute):
xl = pd.ExcelFile('foo.xls')
xl.sheet_names # see all sheet names
xl.parse(sheet_name) # read a specific sheet to DataFrame
see docs for parse for more options...
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Using group by on multiple columns
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Group By X means put all those with the same value for X in the one group.
Group By X, Y means put all those with the same values for both X and Y in the one group.
To illustrate using an example, let's say we have the following table, to do with...
Why is the .bss segment required?
...Imagine that your C program runs on an embedded system, where the code and all constants are saved in true ROM (flash memory). In such systems, an initial "copy-down" must be executed to set all static storage duration objects, before main() is called. It will typically go like this pseudo:
for(i=0...
How to connect to Mysql Server inside VirtualBox Vagrant?
I mounted a new VirtualBox Machine with Vagrant, and inside that VM I installed Mysql Server. How can I connect to that server outside the vm? I already forward the port 3306 of the Vagrantfile , but when I try to connect to the mysql server, it`s resposts with the error:
'reading initial communica...
Eclipse syntax highlighting preferences save and restore
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I finally figured out how to do this.
I just wanted to mention beforehand that I did try to start with a fresh Eclipse install, export the preferences to a .epf file, change just one single setting, export again, and compare the ...
Regex to validate date format dd/mm/yyyy
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Edit February 14th 2019: I've removed a comma that was in the regex which allowed dates like 29-0,-11
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Difference between rake db:migrate db:reset and db:schema:load
...drop, db:setup
db:migrate:reset does db:drop, db:create, db:migrate
Typically, you would use db:migrate after having made changes to the schema via new migration files (this makes sense only if there is already data in the database). db:schema:load is used when you setup a new instance of your app...
Convert line-endings for whole directory tree (Git)
...should be faster. You don't need the -name *.* either, unless you specifically want only files with a period somewhere in the name. That's a windows glob, not a *nix one.
– Useless
Aug 15 '11 at 17:31
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Search and replace in bash using regular expressions
...'s are processed in order. Also, the g flag for the expression will match all occurrences in the input.
You can also pick your favorite tool using this method, i.e. perl, awk, e.g.:
echo "$MYVAR" | perl -pe 's/[a-zA-Z]/X/g and s/[0-9]/N/g'
This may allow you to do more creative matches... For ...