Basic Commands
Create object using the assignment operator (<-, =)
x <- c(1,3,2,5)
x
## [1] 1 3 2 5
x = c(1,6,2)
x
## [1] 1 6 2
y = c(1,4,3)
Using function
length(x) # What does length() do?
## [1] 3
length(y)
## [1] 3
Using +, -, *, /,^ operators
x+y
## [1] 2 10 5
ls() # List objects in the environment
## [1] "x" "y"
rm(x,y) # Remove objects
ls()
## character(0)
rm(list=ls()) # Danger! What does this do? Not recommended!
Matrix operations
?matrix
x=matrix(data=c(1,2,3,4), nrow=2, ncol=2) # Create a 2x2 matrix object
x
## [,1] [,2]
## [1,] 1 3
## [2,] 2 4
x=matrix(c(1,2,3,4),2,2)
matrix(c(1,2,3,4),2,2,byrow=TRUE) # What about byrow=F?
## [,1] [,2]
## [1,] 1 2
## [2,] 3 4
sqrt(x) # What does x look like?
## [,1] [,2]
## [1,] 1.000000 1.732051
## [2,] 1.414214 2.000000
x^2
## [,1] [,2]
## [1,] 1 9
## [2,] 4 16
x=rnorm(50) # Generate a vector of 50 numbers using the rnorm() function
y=x+rnorm(50,mean=50,sd=.1) # What does rnorm(50,mean=50,sd=.1) generate?
cor(x,y) # Correlation of x and y
## [1] 0.9952165
set.seed(1303) # Set the seed for Random Number Generator (RNG) to generate values that are reproducible.
rnorm(50)
## [1] -1.1439763145 1.3421293656 2.1853904757 0.5363925179 0.0631929665
## [6] 0.5022344825 -0.0004167247 0.5658198405 -0.5725226890 -1.1102250073
## [11] -0.0486871234 -0.6956562176 0.8289174803 0.2066528551 -0.2356745091
## [16] -0.5563104914 -0.3647543571 0.8623550343 -0.6307715354 0.3136021252
## [21] -0.9314953177 0.8238676185 0.5233707021 0.7069214120 0.4202043256
## [26] -0.2690521547 -1.5103172999 -0.6902124766 -0.1434719524 -1.0135274099
## [31] 1.5732737361 0.0127465055 0.8726470499 0.4220661905 -0.0188157917
## [36] 2.6157489689 -0.6931401748 -0.2663217810 -0.7206364412 1.3677342065
## [41] 0.2640073322 0.6321868074 -1.3306509858 0.0268888182 1.0406363208
## [46] 1.3120237985 -0.0300020767 -0.2500257125 0.0234144857 1.6598706557
set.seed(3) # Try different seeds?
y=rnorm(100)
Simple descriptive statistics
mean(y)
## [1] 0.01103557
var(y)
## [1] 0.7328675
sqrt(var(y))
## [1] 0.8560768
sd(y)
## [1] 0.8560768
Graphics using R Graphics (without packages)
x=rnorm(100)
y=rnorm(100)
plot(x,y, pch=20, col = "blue") # Scatterplot for two numeric variables by default
plot(x,y, pch=20, col = "blue",xlab="this is the x-axis",ylab="this is the y-axis",main="Plot of X vs Y") # Add labels
pdf("Figure.pdf") # Save as pdf, add a path or it will be stored on the project directory
plot(x,y,col="green") # Try different colors?
dev.off() # Close the file using the dev.off function
## quartz_off_screen
## 2
x=seq(1,10) # Same as x=c(1:10)
x
## [1] 1 2 3 4 5 6 7 8 9 10
x=1:10
x
## [1] 1 2 3 4 5 6 7 8 9 10
x=seq(-pi,pi,length=50)
y=x
Fancy graphs: contour, image, persp (3D)
f=outer(x,y,function(x,y)cos(y)/(1+x^2))
contour(x,y,f)
contour(x,y,f,nlevels=45,add=T)
fa=(f-t(f))/2
contour(x,y,fa,nlevels=15)
image(x,y,fa)
persp(x,y,fa)
persp(x,y,fa,theta=30)
persp(x,y,fa,theta=30,phi=20)
persp(x,y,fa,theta=30,phi=70)
persp(x,y,fa,theta=30,phi=40)
