Getting Started with R

1+1

[1] 2

7-8

[1] -1

#Complex Numbers
(2+5i)+(3-1i)

[1] 5+4i

4/2

[1] 2

6/12

[1] 0.5

2^2

[1] 4

2^5

[1] 32

sqrt(25)

[1] 5

sqrt(16)

[1] 4

sqrt(144)

[1] 12

#Natural Log
log(2)

[1] 0.6931472

log(10)

[1] 2.302585

log(2.72)

[1] 1.000632

# Natural Log
log10(10)

[1] 1

Question 1: Compute the Log base 5 of 10 and the log of 10

# Answers: Question 1
#Log of 10, Base 5
log(10,5) 

[1] 1.430677

#Log of 10, Base 10
log(10,10)

[1] 1

#Log of 100, Base 4
log(100,4)

[1] 3.321928

#Batting Average=(No. of Hits)/(No. of At Bats)
#What is the batting average of a player that bats 29 hits in 112 at bats?
BA=(129)/(412)
BA

[1] 0.3131068

#Alternative Solution
N_Hits=129
At_Bats=412
BA<-N_Hits/At_Bats
BA

[1] 0.3131068

Batting_Average=round(BA,digits = 3)
Batting_Average

[1] 0.313

Question 2: What is the batting average of a player that bats 42 hits in 212 at bats?

# Answers
N_Hits=42
At_Bats1=212
Bat_Average<-N_Hits/At_Bats1
BattingAverage=round(Bat_Average, digits = 3)
BattingAverage

[1] 0.198

#On Base Percentage
#OBP=(H+BB+HBP)/(At Bats+BB+HBP+SF)
#Let us compute the OBP for a player with the following general stats
# AB=515, H=172, BB=88, HBP=5, SF=6
OBP=(172+84+5)/(515+84+5+6)
OBP

[1] 0.4278689

OBP_Adj=round(OBP, digits = 3)
OBP_Adj

[1] 0.428

Question_3: Compute the OBP for a player with the following general stats:

#AB=565, H=156, BB=65, HBP=3, SF=7
OBP=(156+65+3)/(565+65+3+156+7)
OBP_ad=round(OBP, digits = 3)
OBP_ad

[1] 0.281

Often you will want to test whether something is less than, greater than, or equal to something.

3==8

[1] FALSE

2==3

[1] FALSE

1==1

[1] TRUE

3>=1

[1] TRUE

3>=9

[1] FALSE

7<=10

[1] TRUE

7<=6

[1] FALSE

3!=4

[1] TRUE

#Logical Disjunction (or)
FALSE | FALSE # False OR False

[1] FALSE

FALSE | TRUE # False OR True

[1] TRUE

TRUE & FALSE # True AND False

[1] FALSE

!TRUE

[1] FALSE

!FALSE

[1] TRUE

# Combination of statements
2 < 3 | 1 == 5 # 2<3 is True, 1==5 is False, True OR False is True

[1] TRUE

2<1|2==3

[1] FALSE

total_bases<-7+4
total_bases*4

[1] 44

rm(total_bases)
ls()

 [1] "At_Bats"            "At_Bats1"          
 [3] "BA"                 "Bat_Average"       
 [5] "Batting_Average"    "BattingAverage"    
 [7] "N_Hits"             "OBP"               
 [9] "OBP_ad"             "OBP_Adj"           
[11] "pitches_by_innings" "player_positions"  
[13] "strikes_by_innings"

Vectors

pitches_by_innings<-c(12,15,10,20,10)
pitches_by_innings

[1] 12 15 10 20 10

strikes_by_innings<-c(9,12,6,14,9)
strikes_by_innings

[1]  9 12  6 14  9

rep(2,5)

[1] 2 2 2 2 2

rep(3,3)

[1] 3 3 3

1:6

[1] 1 2 3 4 5 6

2:7

[1] 2 3 4 5 6 7

seq(1,10,by=3)

[1]  1  4  7 10

pitches_by_innings+strikes_by_innings 

[1] 21 27 16 34 19

#addition operator

#compare two vectors
pitches_by_innings

[1] 12 15 10 20 10

strikes_by_innings

[1]  9 12  6 14  9

pitches_by_innings==strikes_by_innings

[1] FALSE FALSE FALSE FALSE FALSE

length(pitches_by_innings)

[1] 5

min(pitches_by_innings)

[1] 10

mean(pitches_by_innings)

[1] 13.4

pitches_by_innings[1]

[1] 12

pitches_by_innings[length(pitches_by_innings)]

[1] 10

pitches_by_innings

[1] 12 15 10 20 10

pitches_by_innings[c(1:3)]

[1] 12 15 10

player_positions<-c("catcher", "pitcher", "infielders", "outfielders")
player_positions

[1] "catcher"     "pitcher"     "infielders" 
[4] "outfielders"

Data Frames

data.frame(bonus=c(2,3,1), active_roster=c("yes", "no", "yes"), salary=c(1.5, 2.5, 1))

Using Tables

x<-c("Yes", "No","No","Yes","Yes")
table(x)

x
 No Yes 
  2   3 

Numerical measures and center of spread

ceo_salaries<-c(12,.4,2,15,8,3,1,4,.25)
mean(ceo_salaries)

[1] 5.072222

var(ceo_salaries)

[1] 28.95944

sd(ceo_salaries)

[1] 5.381398

median(ceo_salaries)

[1] 3

fivenum(ceo_salaries)

[1]  0.25  1.00  3.00  8.00 15.00

getMode<-function(x) {
  ux<-unique(x)
  ux[which.max(tabulate(match(x,ux)))]
}

pitches_by_innings

[1] 12 15 10 20 10

getMode(pitches_by_innings)

[1] 10

strikes_by_innings
getMode(strikes_by_innings)

game_day<-c("Saturday","Saturday","Sunday","Monday","Saturday","Tuesday","Sunday","Friday","Friday","Monday")
table(game_day)

game_day
  Friday   Monday Saturday   Sunday  Tuesday 
       2        2        3        2        1 

getMode(game_day)

[1] "Saturday"