V1 Flashcards
R as a calculator
first computing/ algorithm
- Charles Babbage: Analyical Engine
- Ada Lovelace: First Algorithm
- Alan M. Turing: Turing Machine
First Computer
- built 1941, destroyed 1943
- named Z3
- built by Konrad Zuse
- to calculate wing flutter
ENIAC
- Electronic Numerical Integrator and Computer
- electronic general-purpose computer
- Turing-complete
- digital
- capable of being reprogrammed
- loops, branches and subroutines
programming language
low level: - punch cards - assembly mid level: - C high level: - LISP - COBOL
R-Programming language
- free and open source
- statistical computing
- graphics
- written in : R, Fortran, C
- operating system agnostic
- linear and non.linear models
- built-in testing and help
- many add-on packages available (4000+)
exponents (coding)
- 5^2 or 5**2
what is euclidean division + coding
- how often one number fits into the other (39/100, 2 is the euclidean divisor)
- %/%
what is euclidean division remainder + coding
- how often one number fits into the other - what remains after (39/100, 2 is the euclidean divisor, 39*2-> 78 -> 22 left over
%%
special numerical constant (coding)
infinite - inf
NaN - not a number
NA - missing
Built in character constants (coding)
- LETTERS: 26 upper case letters
- letters_ 26 lower case letters
- month.abb: 12 months 3-letter abbreviations
- month.name: 12 months
- pi: ratio of the circumference of a circle to its diameter
imaginary numbers (coding)
as 0i -> instead of sqrt(-1) do sqrt(-1+0i)
basic trigonometry functions (coding)
- sin, cos, tan, asin, etc
logarithms (coding)
log(5) - natural log of 5
log10(5) - base 10 log of 5
exp(1) - e^1
How to manage your Session - Work directive (4)
- getwd(): where does R save/retrieve files
- dir(): what files are there
- setwd(): set another place to save/retrieve files
- Is(): what is in the current environment
How to handle package and save things + end R
- install.packages(“qtl”) - install package
- library(qtl) - load a package
- save(object, file = “Your.RData”) - save object as binary
- save.image(“Your-RData”) - save the whole environment
- q(“no”) - quit the r session
how to use help with functions and terms
- ?functionname - open the help file for function
- ??term search for a term across
types of data (5)
- logical : TRUE, FALSE
- Numeric: 5, 6, 78 …
- Character: “one”, “two” …
- Vector - c (1, 4, 6, 7) - can be numerical, logical or character
Matrix - Y
useful function to deal with data types
- length(): number of elements
- str(): structure of an object
- class(): class or type of an object
- names(): names
- as.: force to a certain type
- is.: is of a certain type
Creating a vector
- c(object, object, …): combine objects into a vector
- seq(from, to, by): a numerical sequence
- rep(object, repeat times): repeat an object / number
Creating a Matrix
- matrix(vector, nrow, ncol): create a matrix from a vector
- cbind(object, object…): combine objects as columns
- rbind(object, object…): combine objects as rows
Indexing a Vector
“A” “B” “C” “D” “E” “F” “G” “H” “I”
V[5] -> “A” “B” “C” “D” “E” “F” “G” “H” “I”
V[2:5] -> “A” “B” “C” “D” “E” “F” “G” “H” “I”
V[c(2:5,8)] -> “A” “B” “C” “D” “E” “F” “G” “H” “I”
Indexing a Matrix
m[1:3, 1] - row 1:3 , column 1 (three)
m[5, 3:6] - row 5, column 3:6 (three)
m[8, 7] - row 9, column 7 (one)
m[, 9] - all of column 9
advances types
- data frame: not a matrix, can contain multiple basic types
- list - not a vector, can contain anything
- factor
- comments (#)
Matrix and data frame functions (5)
nrow() : number of rows ncol(): number of columns rownames(): row names colnames(): columns names t(): transpose
Important about clean code
- use new directory for new lecture
- name files in a logical way
- add a header to each file (comment section): Name, date, purpose of file and copy right
- use a lot of comments and indent where needed
