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Applying a function to every row of a table using dplyr?
...o create an appropriately vectorised function.
R provide pmax which is suitable here, however it also provides Vectorize as a wrapper for mapply to allow you to create a vectorised arbitrary version of an arbitrary function.
library(dplyr)
# use base R pmax (vectorized in C)
iris %>% mutate(max...
Should I use 'border: none' or 'border: 0'?
...they behave in different ways when combined with other rules.
Borders in a table context in collapsing border model
When a table is rendered using border-collapse: collapse, then each rendered border is shared between multiple elements (inner borders are shared among as neighbor cells; outer borders...
How to use GROUP BY to concatenate strings in MySQL?
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SELECT id, GROUP_CONCAT(name SEPARATOR ' ') FROM table GROUP BY id;
http://dev.mysql.com/doc/refman/5.0/en/group-by-functions.html#function_group-concat
From the link above, GROUP_CONCAT: This function returns a string result with the concatenated non-NULL values from a ...
Why the switch statement cannot be applied on strings?
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Additionally, C/C++ switch statements are typically generated as branch tables. It's not nearly as easy to generate a branch table for a string style switch.
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Aggregate / summarize multiple variables per group (e.g. sum, mean)
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Using the data.table package, which is fast (useful for larger datasets)
https://github.com/Rdatatable/data.table/wiki
library(data.table)
df2 <- setDT(df1)[, lapply(.SD, sum), by=.(year, month), .SDcols=c("x1","x2")]
setDF(df2) # con...
Capturing URL parameters in request.GET
...h/?q=CA. The query part '?q=CA' will be automatically reserved in the hash table which you can reference though
request.GET.get('q', None).
Here is an example (file views.py)
class CityListView(generics.ListAPIView):
serializer_class = CityNameSerializer
def get_queryset(self):
if ...
ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock'
...nit.d/mysqld stop
Start MySQL in safe mode
sudo mysqld_safe --skip-grant-tables &
Log into MySQL using root
mysql -uroot
Select the MySQL database to use
use mysql;
Reset the password
-- MySQL version < 5.7
update user set password=PASSWORD("mynewpassword") where User='root';
-- MySQ...
Serializing object that contains cyclic object value
... goes.
One feature that's not as well-known as JSON.stringify() is console.table(). Simply call console.table(whatever);, and it will log the variable in the console in tabular format, making it rather quite easy and convenient to peruse the variable's contents.
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how to generate migration to make references polymorphic
I have a Products table and want to add a column:
4 Answers
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psql - save results of command to a file
I'm using psql's \dt to list all tables in a database and I need to save the results.
10 Answers
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