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Summarizing multiple columns with dplyr? [duplicate]
... a bit with the dplyr-syntax. I have a data frame with different variables and one grouping variable. Now I want to calculate the mean for each column within each group, using dplyr in R.
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Avoiding SQL injection without parameters
...ametrized sql queries in our code. We have two sides in the discussion: Me and some others that say we should always use parameters to safeguard against sql injections and the other guys that don't think it is necessary. Instead they want to replace single apostrophes with two apostrophes in all str...
Difference between database and schema
What's the difference between a Database and a Schema in SQL Server? Both are the containers of tables and data.
5 Answers
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MongoDB and “joins” [duplicate]
...ll only be evaluated when needed. A join (in a SQL database) on the other hand will resolve relationships and return them as if they were a single table (you "join two tables into one").
You can read more about DBRef here:
http://docs.mongodb.org/manual/applications/database-references/
There are ...
Switch to another Git tag
...EAD' state. In this state, "you can look around, make experimental changes and commit them, and [discard those commits] without impacting any branches by performing another checkout".
To retain any changes made, move them to a new branch:
git checkout -b 1.1.4-jspooner
You can get back to the ma...
Why do == comparisons with Integer.valueOf(String) give different results for 127 and 128?
...returning an Integer object, which may have its values cached between -128 and 127. This is why the first value returns true - it's cached - and the second value returns false - 128 isn't a cached value, so you're getting two separate Integer instances.
It is important to note that you are compari...
JavaScript data grid for millions of rows [closed]
...s set to the total height of all the rows. The rows are still being added and removed as the user is scrolling, but the scrolling itself is done by the browser. That allows it to be very fast yet smooth (onscroll events are notoriously slow). The caveat is that there are bugs/limits in the browse...
C++11 introduced a standardized memory model. What does it mean? And how is it going to affect C++ p
C++11 introduced a standardized memory model, but what exactly does that mean? And how is it going to affect C++ programming?
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MFC Grid control 2.27 - C/C++ - 清泛网移动版 - 专注IT技能提升
...快速做出各种定制界面的表格。
Download Grid Control Source and Demo - 311.9 KB
Preface
This grid is the work of thousands of hours of squinting at pixels, hunting memory leaks, adding new features, fixing new bugs and beating the code by force of will into a form that is as f...
MFC Grid control 2.27 - C/C++ - 清泛网移动版 - 专注IT技能提升
...快速做出各种定制界面的表格。
Download Grid Control Source and Demo - 311.9 KB
Preface
This grid is the work of thousands of hours of squinting at pixels, hunting memory leaks, adding new features, fixing new bugs and beating the code by force of will into a form that is as f...