# Basic Values in R

# numeric
class(3.56)
class(2)
# integer
class(2L)
# logical
class(F)
TRUE 
FALSE
T
F
# character
class('salam')

# We always deal with basic values as vectors 
x = c(2,3,5,7,9)
x <- c(2,3,5,7,9)

# = and <- are both assignment operators

class(x) # there is not a new class for vectors
length(x)

y = 1:5
class(y) # integer

# vectorized (element-wise) operations
x * 3
x + y
x > y

z = 51:100
print(z)

# some built-in functions
class()
typeof()
c()

mean(d$k)
min(d$k)
max(d$k)
which.max(d$k)


## How to call values from a vector
# method 1. indexing by integer
z[3]
z[c(3,7,40)]

# method 2. by logical indexing
z > 80
z[z > 80]
z[z > 80 & z < 90]

# method 3. by calling names
t = c(Ali = 15, Mina = 18, Sina = 15)
t
class(t)
t['Ali']
class(t[c('Mina', 'Sina')])

names(t)

a = c(1,3)
names(a) = c('s1', 's2')
a

# Values are mutable in R and can be replaced by new values while calling them
a[2] = 12
a

# a vector has only one class
e = c(1L, 3.6, F, T, 's')
class(e) # takes the most general class among the present values
e

#####################

# matrix
m = 1:100
dim(m) # a vector has no dimention in R
dim(m) = c(20, 5)
m

class(m)
typeof(m) # typeof returns the most general class that an object belongs to

x[c(3, 6, 10),]

# concatenating vectors to build a matrix by row or column
rbind(1:5, 6:10)
cbind(1:5, 6:10)

# list 
x = list(n1 = c(1,2,4),
         n2 = c('a', 'b', 'c', 'd'),
         n3 = 1:20)
class(x)
x
class(x[1]) # [] returns a list
x[[1]]
class(x[[1]]) # [[]] drop the class of the list and returns class the value
x[['n1']]

x$n2 # no need to use '' when we call the names by $

# data.frame
d = data.frame(x = 1:10,
               y = letters[1:10],
               z = LETTERS[1:10],
               k = runif(10, 0, 10))
d
class(d)
# data.frame is a type of list
# it's a list that has been made up of vectors of the same length
typeof(d) # typeof returns the most general class that an object belongs to

# converting matrix to a data.frame
dm = as.data.frame(m)

class(d$x)
d[1,]
d[, 1]
d[1:4, 1:2]

d$x + d$k
d$new_column = 1

d[3, 4] = 40
d[3, 4]