Notes
This posts records all my notes for the online course - Python for Data Science and AI - on Coursera.com.
New notes will be added on the top of the older ones.
Week 2
Logic
- &
- use the
&operator to evaluate AND across a vector.
- use the
- &&
- The
&&version of AND only evaluates the first member of a vector.
- The
|- The
|version of OR evaluates OR across an entire vector
- The
||- the
||version of OR only evaluates the first member of a vector.
- the
- isTRUE(argument)
- The function isTRUE() takes one argument. If that argument evaluates to TRUE, the function will return TRUE. Otherwise, the function will return FALSE.
- xor(argument_1, argument_2)
- The xor() function stands for exclusive OR. If one argument evaluates to TRUE and one argument evaluates to FALSE, then this function will return TRUE, otherwise it will return FALSE.
- which(argument)
- The which() function takes a logical vector as an argument and returns the indices of the vector that are TRUE.
- any(argument)
- The any() function will return TRUE if one or more of the elements in the logical vector is TRUE.
- all(argument)
- The all() function will return TRUE if every element in the logical vector is TRUE.
Week 1
- swirl is a nice place to start. It will teach R programming and data science interactively. Good!
Basics of R
- getwd()
- get the current working directory
- setwd(dir)
- set the current working directory to dir
- file.create(“mytest.R”)
- create new files
- file.exists(“mytest.R”)
- Check to see if “mytest.R” exists in the working directory
- file.info(“mytest.R”)
- Access information about the file “mytest.R”
- file.rename(“mytest.R”, “mytest2.R”)
- Change the name of the file “mytest.R” to “mytest2.R”
- file.copy(“mytest2.R”, “mytest3.R”)
- Make a copy of “mytest2.R” called “mytest3.R”
- file.path(“mytest3.R”)
- Provide the relative path to the file “mytest3.R”
- list.files(), dir()
- list the files in the current working directory
- ls()
- list the current objects
- read.csv(filename)
- read filename.csv
- <-
- equal to ‘=’ in MATLAB
- data$name
- extract parts of an object, i.e. return elements after ‘name’ in ‘data’.
- data[complete.cases(data),]
- return the data frame without NA
- data[!complete.cases(data),]
- return the full data frame
- max(), min(), mean()
- get the maximum, minimum, mean values
