SQL

Adapted from codecademy.com SQL course:

• JOIN will combine rows from different tables if the join condition is true.
• LEFT JOIN will return every row in the left table, and if the join condition is not met, NULL values are used to fill in the columns from the right table.
• Primary key is a column that serves a unique identifier for the rows in the table.
• Foreign key is a column that contains the primary key to another table.
• CROSS JOIN lets us combine all rows of one table with all rows of another table.
• UNION stacks one dataset on top of another.
• WITH allows us to define one or more temporary tables that can be used in the final query.

Learn SQL: Create Table

learn SQL codecademy.com

We learned 6 commands in SQL today;

A statement is a string of characters that the database recognizes as a valid command.

• CREATE TABLE creates a new table.
• INSERT INTO adds a new row to a table.
• SELECT queries data from a table.
• UPDATE edits a row in a table.
• ALTER TABLE changes an existing table.
• DELETE FROM deletes rows from a table

How to crete R Mark Down files in R studio

need to install:
install.package("rmarkdown")

how to render Rmd file through terminal command line after $ssh username

$ echo "rmarkdown::render('sample.Rmd', clean=TRUE)" | R --slave

$ Rscript -e "rmarkdown::render('sample.Rmd', clean=TRUE)”

Need to have "pandoc" package on X11 or Linux machines.
$pandoc -v

solving ODEs

A nice recalling examples here:

http://mathinsight.org/ordinary_differential_equation_introduction