mirror of
https://github.com/adambard/learnxinyminutes-docs.git
synced 2024-12-23 07:12:31 +03:00
Significant new content
I moved some things around. I preserved isomorphismes' "no programming knowledge first" approach; I really like this. In the "programming-heavy" part of the tutorial, I emphasized from the very beginning that every "single" thing in R, like 4 or "foo", is really just a vector of length 1. I added in some whirlwind tours of data.table and ggplot2.
This commit is contained in:
e99n09
parent
754472044b
commit
31c74615e6
460
r.html.markdown
460
r.html.markdown
@ -6,34 +6,42 @@ contributors:
|
||||
filename: learnr.r
|
||||
---
|
||||
|
||||
R is a statistical computing language. It has lots of libraries for uploading and cleaning data sets, running statistical procedures, and making graphs. You can also run `R`commands within a LaTeX document.
|
||||
R is a statistical computing language. It has lots of libraries for uploading and cleaning data sets, running statistical procedures, and making graphs. You can also run `R` commands within a LaTeX document.
|
||||
|
||||
```python
|
||||
|
||||
# Comments start with number symbols.
|
||||
|
||||
# You can't make a multi-line comment per se,
|
||||
# You can't make multi-line comments,
|
||||
# but you can stack multiple comments like so.
|
||||
|
||||
# in Windows, hit COMMAND-ENTER to execute a line
|
||||
# in Windows or Mac, hit COMMAND-ENTER to execute a line
|
||||
|
||||
|
||||
###################################################################
|
||||
|
||||
#############################################################################
|
||||
# Stuff you can do without understanding anything about programming
|
||||
###################################################################
|
||||
#############################################################################
|
||||
|
||||
data() # Browse pre-loaded data sets
|
||||
data(rivers) # Lengths of Major North American Rivers
|
||||
ls() # Notice that "rivers" appears in the workspace
|
||||
head(rivers) # peek at the dataset
|
||||
# In this section, we show off some of the cool stuff you can do in
|
||||
# R without understanding anything about programming. Do not worry
|
||||
# about understanding everything the code does. Just enjoy!
|
||||
|
||||
data() # browse pre-loaded data sets
|
||||
data(rivers) # get this one: "Lengths of Major North American Rivers"
|
||||
ls() # notice that "rivers" now appears in the workspace
|
||||
head(rivers) # peek at the data set
|
||||
# 735 320 325 392 524 450
|
||||
|
||||
length(rivers) # how many rivers were measured?
|
||||
# 141
|
||||
summary(rivers)
|
||||
summary(rivers) # what are some summary statistics?
|
||||
# Min. 1st Qu. Median Mean 3rd Qu. Max.
|
||||
# 135.0 310.0 425.0 591.2 680.0 3710.0
|
||||
stem(rivers) #stem-and-leaf plot (like a histogram)
|
||||
#
|
||||
|
||||
# make a stem-and-leaf plot (a histogram-like data visualization)
|
||||
stem(rivers)
|
||||
|
||||
# The decimal point is 2 digit(s) to the right of the |
|
||||
#
|
||||
# 0 | 4
|
||||
@ -56,8 +64,8 @@ stem(rivers) #stem-and-leaf plot (like a histogram)
|
||||
# 34 |
|
||||
# 36 | 1
|
||||
|
||||
|
||||
stem(log(rivers)) #Notice that the data are neither normal nor log-normal! Take that, Bell Curve fundamentalists.
|
||||
stem(log(rivers)) # Notice that the data are neither normal nor log-normal!
|
||||
# Take that, Bell curve fundamentalists.
|
||||
|
||||
# The decimal point is 1 digit(s) to the left of the |
|
||||
#
|
||||
@ -80,17 +88,19 @@ stem(log(rivers)) #Notice that the data are neither normal nor log-normal! Take
|
||||
# 80 |
|
||||
# 82 | 2
|
||||
|
||||
# make a histogram:
|
||||
hist(rivers, col="#333333", border="white", breaks=25) # play around with these parameters
|
||||
hist(log(rivers), col="#333333", border="white", breaks=25) # you'll do more plotting later
|
||||
|
||||
hist(rivers, col="#333333", border="white", breaks=25) #play around with these parameters
|
||||
hist(log(rivers), col="#333333", border="white", breaks=25) #you'll do more plotting later
|
||||
|
||||
#Here's another neat data set that comes pre-loaded. R has tons of these. data()
|
||||
# Here's another neat data set that comes pre-loaded. R has tons of these.
|
||||
data(discoveries)
|
||||
plot(discoveries, col="#333333", lwd=3, xlab="Year", main="Number of important discoveries per year")
|
||||
plot(discoveries, col="#333333", lwd=3, type = "h", xlab="Year", main="Number of important discoveries per year")
|
||||
plot(discoveries, col="#333333", lwd=3, xlab="Year",
|
||||
main="Number of important discoveries per year")
|
||||
plot(discoveries, col="#333333", lwd=3, type = "h", xlab="Year",
|
||||
main="Number of important discoveries per year")
|
||||
|
||||
|
||||
#rather than leaving the default ordering (by year) we could also sort to see what's typical
|
||||
# Rather than leaving the default ordering (by year),
|
||||
# we could also sort to see what's typical:
|
||||
sort(discoveries)
|
||||
# [1] 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 2 2 2 2
|
||||
# [26] 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 3 3 3
|
||||
@ -117,231 +127,249 @@ stem(discoveries, scale=2)
|
||||
|
||||
max(discoveries)
|
||||
# 12
|
||||
|
||||
summary(discoveries)
|
||||
# Min. 1st Qu. Median Mean 3rd Qu. Max.
|
||||
# 0.0 2.0 3.0 3.1 4.0 12.0
|
||||
|
||||
|
||||
|
||||
|
||||
#Basic statistical operations don't require any programming knowledge either
|
||||
|
||||
#roll a die a few times
|
||||
# Roll a die a few times
|
||||
round(runif(7, min=.5, max=6.5))
|
||||
# 1 4 6 1 4 6 4
|
||||
# Your numbers will differ from mine unless we set the same random.seed(31337)
|
||||
|
||||
#your numbers will differ from mine unless we set the same random.seed(31337)
|
||||
|
||||
|
||||
#draw from a standard Gaussian 9 times
|
||||
# Draw from a standard Gaussian 9 times
|
||||
rnorm(9)
|
||||
# [1] 0.07528471 1.03499859 1.34809556 -0.82356087 0.61638975 -1.88757271
|
||||
# [7] -0.59975593 0.57629164 1.08455362
|
||||
|
||||
|
||||
|
||||
##################################################
|
||||
# Data types and basic arithmetic
|
||||
##################################################
|
||||
|
||||
# Now for the programming-oriented part of the tutorial.
|
||||
# In this section you will meet the important data types of R:
|
||||
# integers, numerics, characters, logicals, and factors.
|
||||
# There are others, but these are the bare minimum you need to
|
||||
# get started.
|
||||
|
||||
# INTEGERS
|
||||
# Long-storage integers are written with L
|
||||
5L # 5
|
||||
class(5L) # "integer"
|
||||
# (Try ?class for more information on the class() function.)
|
||||
# In R, every single value, like 5L, is considered a vector of length 1
|
||||
length(5L) # 1
|
||||
# You can have an integer vector with length > 1 too:
|
||||
c(4L, 5L, 8L, 3L) # 4 5 8 3
|
||||
length(c(4L, 5L, 8L, 3L)) # 4
|
||||
class(c(4L, 5L, 8L, 3L)) # "integer"
|
||||
|
||||
|
||||
|
||||
|
||||
#########################
|
||||
# Basic programming stuff
|
||||
#########################
|
||||
|
||||
# NUMBERS
|
||||
|
||||
# "numeric" means double-precision floating-point numbers
|
||||
5 # 5
|
||||
class(5) # "numeric"
|
||||
5e4 # 50000 #handy when dealing with large,small,or variable orders of magnitude
|
||||
6.02e23 # Avogadro's number
|
||||
1.6e-35 # Planck length
|
||||
|
||||
# long-storage integers are written with L
|
||||
5L # 5
|
||||
class(5L) # "integer"
|
||||
|
||||
# Try ?class for more information on the class() function
|
||||
# In fact, you can look up the documentation on `xyz` with ?xyz
|
||||
# or see the source for `xyz` by evaluating xyz
|
||||
|
||||
# Arithmetic
|
||||
10 + 66 # 76
|
||||
53.2 - 4 # 49.2
|
||||
2 * 2.0 # 4
|
||||
3L / 4 # 0.75
|
||||
3 %% 2 # 1
|
||||
|
||||
# Weird number types
|
||||
class(NaN) # "numeric"
|
||||
# NUMERICS
|
||||
# A "numeric" is a double-precision floating-point number
|
||||
5 # 5
|
||||
class(5) # "numeric"
|
||||
# Again, everything in R is a vector;
|
||||
# you can make a numeric vector with more than one element
|
||||
c(3,3,3,2,2,1) # 3 3 3 2 2 1
|
||||
# You can use scientific notation too
|
||||
5e4 # 50000
|
||||
6.02e23 # Avogadro's number
|
||||
1.6e-35 # Planck length
|
||||
# You can also have infinitely large or small numbers
|
||||
class(Inf) # "numeric"
|
||||
class(-Inf) # "numeric" #used in for example integrate( dnorm(x), 3, Inf ) -- which obviates Z-score tables
|
||||
|
||||
# but beware, NaN isn't the only weird type...
|
||||
class(NA) # see below
|
||||
class(NULL) # NULL
|
||||
|
||||
|
||||
# SIMPLE LISTS
|
||||
c(6, 8, 7, 5, 3, 0, 9) # 6 8 7 5 3 0 9
|
||||
c('alef', 'bet', 'gimmel', 'dalet', 'he') # "alef" "bet" "gimmel" "dalet" "he"
|
||||
c('Z', 'o', 'r', 'o') == "Zoro" # FALSE FALSE FALSE FALSE
|
||||
|
||||
#some more nice built-ins
|
||||
5:15 # 5 6 7 8 9 10 11 12 13 14 15
|
||||
|
||||
seq(from=0, to=31337, by=1337)
|
||||
# [1] 0 1337 2674 4011 5348 6685 8022 9359 10696 12033 13370 14707
|
||||
# [13] 16044 17381 18718 20055 21392 22729 24066 25403 26740 28077 29414 30751
|
||||
|
||||
letters
|
||||
# [1] "a" "b" "c" "d" "e" "f" "g" "h" "i" "j" "k" "l" "m" "n" "o" "p" "q" "r" "s"
|
||||
# [20] "t" "u" "v" "w" "x" "y" "z"
|
||||
|
||||
month.abb # "Jan" "Feb" "Mar" "Apr" "May" "Jun" "Jul" "Aug" "Sep" "Oct" "Nov" "Dec"
|
||||
|
||||
|
||||
# Access the n'th element of a list with list.name[n] or sometimes list.name[[n]]
|
||||
letters[18] # "r"
|
||||
LETTERS[13] # "M"
|
||||
month.name[9] # "September"
|
||||
c(6, 8, 7, 5, 3, 0, 9)[3] # 7
|
||||
|
||||
class(-Inf) # "numeric"
|
||||
# You might use "Inf", for example, in integrate( dnorm(x), 3, Inf);
|
||||
# this obviates Z-score tables.
|
||||
|
||||
# BASIC ARITHMETIC
|
||||
# You can do arithmetic with numbers
|
||||
# Doing arithmetic on a mix of integers and numerics gives you another numeric
|
||||
10L + 66L # 76 # integer plus integer gives integer
|
||||
53.2 - 4 # 49.2 # numeric minus numeric gives numeric
|
||||
2.0 * 2L # 4 # numeric times integer gives numeric
|
||||
3L / 4 # 0.75 # integer over integer gives numeric
|
||||
3 %% 2 # 1 # the remainder of two numerics is another numeric
|
||||
# Illegal arithmetic yeilds you a "not-a-number":
|
||||
0 / 0 # NaN
|
||||
class(NaN) # "numeric"
|
||||
# You can do arithmetic on two vectors with length greater than 1,
|
||||
# so long as the larger vector's length is an integer multiple of the smaller
|
||||
c(1,2,3) + c(1,2,3) # 2 4 6
|
||||
|
||||
# CHARACTERS
|
||||
|
||||
# There's no difference between strings and characters in R
|
||||
|
||||
"Horatio" # "Horatio"
|
||||
"Horatio" # "Horatio"
|
||||
class("Horatio") # "character"
|
||||
substr("Fortuna multis dat nimis, nulli satis.", 9, 15) # "multis "
|
||||
gsub('u', 'ø', "Fortuna multis dat nimis, nulli satis.") # "Fortøna møltis dat nimis, nølli satis."
|
||||
|
||||
|
||||
class('H') # "character"
|
||||
# Those were both character vectors of length 1
|
||||
# Here is a longer one:
|
||||
c('alef', 'bet', 'gimmel', 'dalet', 'he')
|
||||
# =>
|
||||
# "alef" "bet" "gimmel" "dalet" "he"
|
||||
length(c("Call","me","Ishmael")) # 3
|
||||
# You can do regex operations on character vectors:
|
||||
substr("Fortuna multis dat nimis, nulli satis.", 9, 15) # "multis "
|
||||
gsub('u', 'ø', "Fortuna multis dat nimis, nulli satis.") # "Fortøna møltis dat nimis, nølli satis."
|
||||
# R has several built-in character vectors:
|
||||
letters
|
||||
# =>
|
||||
# [1] "a" "b" "c" "d" "e" "f" "g" "h" "i" "j" "k" "l" "m" "n" "o" "p" "q" "r" "s"
|
||||
# [20] "t" "u" "v" "w" "x" "y" "z"
|
||||
month.abb # "Jan" "Feb" "Mar" "Apr" "May" "Jun" "Jul" "Aug" "Sep" "Oct" "Nov" "Dec"
|
||||
|
||||
# LOGICALS
|
||||
|
||||
# booleans
|
||||
# In R, a "logical" is a boolean
|
||||
class(TRUE) # "logical"
|
||||
class(FALSE) # "logical"
|
||||
# Behavior is normal
|
||||
# Their behavior is normal
|
||||
TRUE == TRUE # TRUE
|
||||
TRUE == FALSE # FALSE
|
||||
FALSE != FALSE # FALSE
|
||||
FALSE != TRUE # TRUE
|
||||
# Missing data (NA) is logical, too
|
||||
class(NA) # "logical"
|
||||
|
||||
|
||||
# Here we get a logical vector with many elements:
|
||||
c('Z', 'o', 'r', 'r', 'o') == "Zorro" # FALSE FALSE FALSE FALSE FALSE
|
||||
c('Z', 'o', 'r', 'r', 'o') == "Z" # TRUE FALSE FALSE FALSE FALSE
|
||||
|
||||
# FACTORS
|
||||
|
||||
# The factor class is for categorical data
|
||||
# which can be ordered (like childrens' grade levels)
|
||||
# or unordered (like gender)
|
||||
levels(factor(c("female", "male", "male", "female", "NA", "female"))) # "female" "male" "NA"
|
||||
|
||||
# Factors can be ordered (like childrens' grade levels) or unordered (like gender)
|
||||
factor(c("female", "female", "male", "NA", "female"))
|
||||
# female female male NA female
|
||||
# Levels: female male NA
|
||||
# The "levels" are the values the categorical data can take
|
||||
levels(factor(c("male", "male", "female", "NA", "female"))) # "female" "male" "NA"
|
||||
# If a factor has length 1, its levels will have length 1, too
|
||||
length(factor("male")) # 1
|
||||
length(levels(factor("male"))) # 1
|
||||
# Factors are commonly seen in data frames, a data structure we will cover later
|
||||
# in this tutorial:
|
||||
data(infert) # "Infertility after Spontaneous and Induced Abortion"
|
||||
levels(infert$education) # "0-5yrs" "6-11yrs" "12+ yrs"
|
||||
|
||||
data(infert) #Infertility after Spontaneous and Induced Abortion
|
||||
levels(infert$education) # "0-5yrs" "6-11yrs" "12+ yrs"
|
||||
# WEIRD TYPES
|
||||
# A quick summary of some of the weirder types in R
|
||||
class(Inf) # "numeric"
|
||||
class(-Inf) # "numeric"
|
||||
class(NaN) # "numeric"
|
||||
class(NA) # "logical"
|
||||
class(NULL) # NULL
|
||||
|
||||
# TYPE COERCION
|
||||
# Type-coercion is when you force a value to take on a different type
|
||||
as.character(c(6, 8)) # "6" "8"
|
||||
as.logical(c(1,0,1,1)) # TRUE FALSE TRUE TRUE
|
||||
# If you put elements of different classes into a vector, weird coercions happen:
|
||||
c(TRUE, 4) # 1 4
|
||||
c("dog", TRUE, 4) # "dog" "TRUE" "4"
|
||||
as.numeric("Bilbo")
|
||||
# =>
|
||||
# [1] NA
|
||||
# Warning message:
|
||||
# NAs introduced by coercion
|
||||
|
||||
# Also note: those were just the basic data types
|
||||
# There are many more data types, such as for dates, time series, etc.
|
||||
|
||||
|
||||
|
||||
##################################################
|
||||
# Variables, loops, if/else
|
||||
##################################################
|
||||
|
||||
# A variable is like a box you store a value in for later use.
|
||||
# We call this "assigning" the value to the variable.
|
||||
# Having variables lets us write loops, functions, and if/else statements
|
||||
|
||||
# VARIABLES
|
||||
|
||||
# Lots of way to assign stuff
|
||||
# Lots of way to assign stuff:
|
||||
x = 5 # this is possible
|
||||
y <- "1" # this is preferred
|
||||
TRUE -> z # this works but is weird
|
||||
|
||||
# We can use coerce variables to different classes
|
||||
as.numeric(y) # 1
|
||||
as.character(x) # "5"
|
||||
|
||||
# LOOPS
|
||||
|
||||
# We've got for loops
|
||||
for (i in 1:4) {
|
||||
print(i)
|
||||
}
|
||||
|
||||
# We've got while loops
|
||||
a <- 10
|
||||
while (a > 4) {
|
||||
cat(a, "...", sep = "")
|
||||
a <- a - 1
|
||||
}
|
||||
|
||||
# Keep in mind that for and while loops run slowly in R
|
||||
# Operations on entire vectors (i.e. a whole row, a whole column)
|
||||
# or apply()-type functions (we'll discuss later) are preferred
|
||||
|
||||
# IF/ELSE
|
||||
|
||||
# Again, pretty standard
|
||||
if (4 > 3) {
|
||||
print("Huzzah! It worked!")
|
||||
print("4 is greater than 3")
|
||||
} else {
|
||||
print("Noooo! This is blatantly illogical!")
|
||||
print("4 is not greater than 3")
|
||||
}
|
||||
# =>
|
||||
# [1] "Huzzah! It worked!"
|
||||
# [1] "4 is greater than 3"
|
||||
|
||||
# FUNCTIONS
|
||||
|
||||
# Defined like so:
|
||||
jiggle <- function(x) {
|
||||
x = x + rnorm(1, sd=.1) #add in a bit of (controlled) noise
|
||||
return(x)
|
||||
}
|
||||
|
||||
# Called like any other R function:
|
||||
jiggle(5) # 5±ε. After set.seed(2716057), jiggle(5)==5.005043
|
||||
|
||||
#########################
|
||||
# Fun with data: vectors, matrices, data frames, and arrays
|
||||
#########################
|
||||
|
||||
|
||||
###########################################################################
|
||||
# Data structures: Vectors, matrices, data frames, and arrays
|
||||
###########################################################################
|
||||
|
||||
# ONE-DIMENSIONAL
|
||||
|
||||
# You can vectorize anything, so long as all components have the same type
|
||||
# Let's start from the very beginning, and with something you already know: vectors.
|
||||
# As explained above, every single element in R is already a vector
|
||||
# Make sure the elements of long vectors all have the same type
|
||||
vec <- c(8, 9, 10, 11)
|
||||
vec # 8 9 10 11
|
||||
# The class of a vector is the class of its components
|
||||
class(vec) # "numeric"
|
||||
# If you vectorize items of different classes, weird coercions happen
|
||||
c(TRUE, 4) # 1 4
|
||||
c("dog", TRUE, 4) # "dog" "TRUE" "4"
|
||||
|
||||
# We ask for specific components like so (R starts counting from 1)
|
||||
vec[1] # 8
|
||||
# We ask for specific elements by subsetting with square brackets
|
||||
# (Note that R starts counting from 1)
|
||||
vec[1] # 8
|
||||
letters[18] # "r"
|
||||
LETTERS[13] # "M"
|
||||
month.name[9] # "September"
|
||||
c(6, 8, 7, 5, 3, 0, 9)[3] # 7
|
||||
# We can also search for the indices of specific components,
|
||||
which(vec %% 2 == 0) # 1 3
|
||||
# or grab just the first or last entry in the vector
|
||||
# grab just the first or last entry in the vector,
|
||||
head(vec, 1) # 8
|
||||
tail(vec, 1) # 11
|
||||
# or figure out if a certain value is in the vector
|
||||
any(vec == 10) # TRUE
|
||||
# If an index "goes over" you'll get NA:
|
||||
vec[6] # NA
|
||||
# You can find the length of your vector with length()
|
||||
length(vec) # 4
|
||||
|
||||
# You can perform operations on entire vectors or subsets of vectors
|
||||
vec * 4 # 16 20 24 28
|
||||
vec[2:3] * 5 # 25 30
|
||||
any(vec[2:3] == 8) # FALSE
|
||||
# and there are many built-in functions to summarize vectors
|
||||
mean(vec) # 9.5
|
||||
var(vec) # 1.666667
|
||||
sd(vec) # 1.290994
|
||||
sd(vec) # 1.290994
|
||||
max(vec) # 11
|
||||
min(vec) # 8
|
||||
sum(vec) # 38
|
||||
# Some more nice built-ins:
|
||||
5:15 # 5 6 7 8 9 10 11 12 13 14 15
|
||||
seq(from=0, to=31337, by=1337)
|
||||
# [1] 0 1337 2674 4011 5348 6685 8022 9359 10696 12033 13370 14707
|
||||
# [13] 16044 17381 18718 20055 21392 22729 24066 25403 26740 28077 29414 30751
|
||||
|
||||
# TWO-DIMENSIONAL (ALL ONE CLASS)
|
||||
|
||||
@ -361,6 +389,7 @@ mat[1,] # 1 4
|
||||
3 * mat[,1] # 3 6 9
|
||||
# Ask for a specific cell
|
||||
mat[3,2] # 6
|
||||
|
||||
# Transpose the whole matrix
|
||||
t(mat)
|
||||
# =>
|
||||
@ -368,6 +397,14 @@ t(mat)
|
||||
# [1,] 1 2 3
|
||||
# [2,] 4 5 6
|
||||
|
||||
# Matrix multiplication
|
||||
mat %*% t(mat)
|
||||
# =>
|
||||
# [,1] [,2] [,3]
|
||||
# [1,] 17 22 27
|
||||
# [2,] 22 29 36
|
||||
# [3,] 27 36 45
|
||||
|
||||
# cbind() sticks vectors together column-wise to make a matrix
|
||||
mat2 <- cbind(1:4, c("dog", "cat", "bird", "dog"))
|
||||
mat2
|
||||
@ -395,24 +432,85 @@ mat3
|
||||
# TWO-DIMENSIONAL (DIFFERENT CLASSES)
|
||||
|
||||
# For columns of different classes, use the data frame
|
||||
dat <- data.frame(c(5,2,1,4), c("dog", "cat", "bird", "dog"))
|
||||
names(dat) <- c("number", "species") # name the columns
|
||||
class(dat) # "data.frame"
|
||||
dat
|
||||
# This data structure is so useful for statistical programming,
|
||||
# a version of it was added to Python in the package "pandas".
|
||||
|
||||
students <- data.frame(c("Cedric","Fred","George","Cho","Draco","Ginny"),
|
||||
c(3,2,2,1,0,-1),
|
||||
c("H", "G", "G", "R", "S", "G"))
|
||||
names(students) <- c("name", "year", "house") # name the columns
|
||||
class(students) # "data.frame"
|
||||
students
|
||||
# =>
|
||||
# number species
|
||||
# 1 5 dog
|
||||
# 2 2 cat
|
||||
# 3 1 bird
|
||||
# 4 4 dog
|
||||
class(dat$number) # "numeric"
|
||||
class(dat[,2]) # "factor"
|
||||
# name year house
|
||||
# 1 Cedric 3 H
|
||||
# 2 Fred 2 G
|
||||
# 3 George 2 G
|
||||
# 4 Cho 1 R
|
||||
# 5 Draco 0 S
|
||||
# 6 Ginny -1 G
|
||||
class(students$year) # "numeric"
|
||||
class(students[,3]) # "factor"
|
||||
# find the dimensions
|
||||
nrow(students) # 6
|
||||
ncol(students) # 3
|
||||
dim(students) # 6 3
|
||||
# The data.frame() function converts character vectors to factor vectors
|
||||
# by default; turn this off by setting stringsAsFactors = FALSE when
|
||||
# you create the data.frame
|
||||
?data.frame
|
||||
|
||||
# There are many twisty ways to subset data frames, all subtly unalike
|
||||
dat$number # 5 2 1 4
|
||||
dat[,1] # 5 2 1 4
|
||||
dat[,"number"] # 5 2 1 4
|
||||
students$year # 3 2 2 1 0 -1
|
||||
students[,2] # 3 2 2 1 0 -1
|
||||
students[,"year"] # 3 2 2 1 0 -1
|
||||
|
||||
# A popular replacement for the data.frame structure is the data.table
|
||||
# If you're working with huge or panel data, or need to merge a few data
|
||||
# sets, data.table can be a good choice. Here's a whirlwind tour:
|
||||
install.packages("data.table")
|
||||
require(data.table)
|
||||
students <- as.data.table(students)
|
||||
students # note the slightly different print-out
|
||||
# =>
|
||||
# name year house
|
||||
# 1: Cedric 3 H
|
||||
# 2: Fred 2 G
|
||||
# 3: George 2 G
|
||||
# 4: Cho 1 R
|
||||
# 5: Draco 0 S
|
||||
# 6: Ginny -1 G
|
||||
students[name=="Ginny"]
|
||||
# =>
|
||||
# name year house
|
||||
# 1: Ginny -1 G
|
||||
students[year==2]
|
||||
# =>
|
||||
# name year house
|
||||
# 1: Fred 2 G
|
||||
# 2: George 2 G
|
||||
founders <- data.table(house=c("G","H","R","S"),
|
||||
founder=c("Godric","Helga","Rowena","Salazar"))
|
||||
founders
|
||||
# =>
|
||||
# house founder
|
||||
# 1: G Godric
|
||||
# 2: H Helga
|
||||
# 3: R Rowena
|
||||
# 4: S Salazar
|
||||
setkey(students, house)
|
||||
setkey(founders, house)
|
||||
students <- founders[students] # merge the two data sets
|
||||
setnames(students, c("house","houseFounderName","studentName","year"))
|
||||
students[,order(c("name","year","house","houseFounderName")), with=F]
|
||||
# =>
|
||||
# studentName year house houseFounderName
|
||||
# 1: Fred 2 G Godric
|
||||
# 2: George 2 G Godric
|
||||
# 3: Ginny -1 G Godric
|
||||
# 4: Cedric 3 H Helga
|
||||
# 5: Cho 1 R Rowena
|
||||
# 6: Draco 0 S Salazar
|
||||
|
||||
# MULTI-DIMENSIONAL (ALL OF ONE CLASS)
|
||||
|
||||
@ -446,15 +544,23 @@ array(c(c(c(2,300,4),c(8,9,0)),c(c(5,60,0),c(66,7,847))), dim=c(3,2,2))
|
||||
list1 <- list(time = 1:40)
|
||||
list1$price = c(rnorm(40,.5*list1$time,4)) # random
|
||||
list1
|
||||
|
||||
# You can get items in the list like so
|
||||
list1$time
|
||||
# You can subset list items like vectors
|
||||
list1$time # one way
|
||||
list1[["time"]] # another way
|
||||
list1[[1]] # yet another way
|
||||
# =>
|
||||
# [1] 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33
|
||||
# [34] 34 35 36 37 38 39 40
|
||||
# You can subset list items like any other vector
|
||||
list1$price[4]
|
||||
|
||||
#########################
|
||||
# Lists are not the most efficient data structure to work with in R;
|
||||
# unless you have a very good reason, you should stick to data.frames
|
||||
# Lists are often returned by functions that perform linear regressions
|
||||
|
||||
##################################################
|
||||
# The apply() family of functions
|
||||
#########################
|
||||
##################################################
|
||||
|
||||
# Remember mat?
|
||||
mat
|
||||
@ -467,7 +573,7 @@ mat
|
||||
# over rows (MAR = 1) or columns (MAR = 2)
|
||||
# That is, R does FUN to each row (or column) of X, much faster than a
|
||||
# for or while loop would do
|
||||
apply(mat, MAR = 2, myFunc)
|
||||
apply(mat, MAR = 2, jiggle)
|
||||
# =>
|
||||
# [,1] [,2]
|
||||
# [1,] 3 15
|
||||
@ -478,16 +584,18 @@ apply(mat, MAR = 2, myFunc)
|
||||
# Don't feel too intimidated; everyone agrees they are rather confusing
|
||||
|
||||
# The plyr package aims to replace (and improve upon!) the *apply() family.
|
||||
|
||||
install.packages("plyr")
|
||||
require(plyr)
|
||||
?plyr
|
||||
|
||||
|
||||
|
||||
#########################
|
||||
# Loading data
|
||||
#########################
|
||||
|
||||
# "pets.csv" is a file on the internet
|
||||
# (but it could just as easily be be a file on your own computer)
|
||||
pets <- read.csv("http://learnxinyminutes.com/docs/pets.csv")
|
||||
pets
|
||||
head(pets, 2) # first two rows
|
||||
@ -499,10 +607,13 @@ write.csv(pets, "pets2.csv") # to make a new .csv file
|
||||
|
||||
# Try ?read.csv and ?write.csv for more information
|
||||
|
||||
|
||||
|
||||
#########################
|
||||
# Plots
|
||||
#########################
|
||||
|
||||
# BUILT-IN PLOTTING FUNCTIONS
|
||||
# Scatterplots!
|
||||
plot(list1$time, list1$price, main = "fake data")
|
||||
# Regressions!
|
||||
@ -512,18 +623,25 @@ linearModel # outputs result of regression
|
||||
abline(linearModel, col = "red")
|
||||
# Get a variety of nice diagnostics
|
||||
plot(linearModel)
|
||||
|
||||
# Histograms!
|
||||
hist(rpois(n = 10000, lambda = 5), col = "thistle")
|
||||
|
||||
# Barplots!
|
||||
barplot(c(1,4,5,1,2), names.arg = c("red","blue","purple","green","yellow"))
|
||||
|
||||
# GGPLOT2
|
||||
# But these are not even the prettiest of R's plots
|
||||
# Try the ggplot2 package for more and better graphics
|
||||
|
||||
install.packages("ggplot2")
|
||||
require(ggplot2)
|
||||
?ggplot2
|
||||
pp <- ggplot(students, aes(x=house))
|
||||
pp + geom_histogram()
|
||||
ll <- as.data.table(list1)
|
||||
pp <- ggplot(ll, aes(x=time,price))
|
||||
pp + geom_point()
|
||||
# ggplot2 has excellent documentation (available http://docs.ggplot2.org/current/)
|
||||
|
||||
|
||||
|
||||
```
|
||||
|
||||
|
||||
Loading…
Reference in New Issue
Block a user