Reference : Jared P.Lander, R for Everyone: Advanced Analytics and Graphics

2. Kan, Hao-Cheng
Lunghwa University of Science and Technology
http://kanchengzxdfgcv.blogspot.tw/

6. > as.numeric(TRUE)
> as.numeric(FALSE)
> as.character(TRUE)
> as.character(FALSE)
> as.factor(TRUE)
> as.factor(FALSE)
>
> k = "kan"
> class(k)
> as.character(k)
>
> n = 123
> class(n)
> as.numeric(n)
>
> test = as.numeric(k)
> test

7. > 1 == 1
> 1 < 1
> 1 <= 1
> 1 > 1
> 1 >= 1
> 1 != 1
> toCheck = 1
if (toCheck == 1)
{
print("hello")
}
if (toCheck == 0)
{
print("hello")
}

8. check.bool = function(x){
if (x == 1){
print("hello")
}else{
print("goodbye")
}
}
> check.bool(1)
> check.bool(0)
> check.bool("k")
> check.bool(TRUE)

9. check.bool = function(x){
if (x == 1){
print("hello")
} else if (x == 0){
print("goodbye")
} else{
print("confused")
}
}
> check.bool(1)
> check.bool(0)
> check.bool(2)
> check.bool("k")

11. use.switch = function(x){
switch(x,
"a"="first",
"b"="second",
"z"="last",
"c"="third",
"other")
}
> use.switch("a")
> use.switch("b")
> use.switch("c")
> use.switch("d")
> use.switch("OwO")
> use.switch("z")
> use.switch(1)
> use.switch(2)
> use.switch(3)
> use.switch(4)
> use.switch(5)
> use.switch(6)
> is.null(use.switch(6))

13. > ifelse(1 == 1, "Yes", "No")
> ifelse(1 == 0, "Yes", "No")
>
> toTest = c(1, 1, 0, 1, 0, 1)
> class(toTest)
> toTest
>
> ifelse(toTest == 1, "Yes", "No")
> ifelse(toTest == 1, toTest * 3, toTest)
> ifelse(toTest == 1, toTest * 3, "Zero")
>
> toTest[2] = NA
> class(toTest)
> toTest
>
> ifelse(toTest == 1, "Yes", "No")
> ifelse(toTest == 1, toTest * 3, toTest)
> ifelse(toTest == 1, toTest * 3, "Zero")

15. > a = c(1, 1, 0, 1)
> b = c(2, 1, 0, 1)
> bs = c(2, 1, 0, 1)
>
> ifelse(a == 1 & b == 1, "Yes", "No")
> ifelse(a == 1 && b == 1, "Yes", "No")
> ifelse(a == 1 && bs == 1, "Yes", "No")
ifelse(a == 1 & b == 1, "Yes", "No") ifelse(a == 1 && b == 1, "Yes", "No")

18. squfc = function(xsqu,ysqu){
if( xsqu <= 0 || ysqu <= 0|| is.na(xsqu) || is.na( ysqu) || is.character(xsqu) ||is.character(ysqu)){
print(NA)
}else{
squmatem = xsqu * ysqu
return(squmatem)
}
}

19. > squfc( 3, 4)
> squfc( 0, 4)
> squfc( 3, 0)
> squfc( 3, NA)
> squfc( NA, 4)
> squfc( 3, "Hi")
> squfc( "Hi", 4)
>
> ww = c(1,NA,3,4,5)
> qq = c(6,7,NA,9,10)
> squfc(ww,qq)