.chapter5<-function(i=0){
" i  Chapter 5: R loops and various conditions
  -  -------------------------------------
  1  Loop: Simple for loops 
  2      : Double for loops
  3      : while loop
  4      : infinitive loop
  5      : How to stop an infinitive loop
  6      : break
  7      : Length of a vector and dimension of a matrix 
  8      : Loops vs. matrix manipulation 
  9      : Complex examples 
 10  Conditioins: if stop
 11             : if statement 
 12             : ifelse() function 
 13             : if esle() function 
 14             : if else if() function 
 15  logic 'OR'
 16  logic 'and' 
 17  (a and b) or (c and d)
 18   Embedded conditions 
 19  Videos
 20  Links

 Example #1:>.c5    # see the above list
 Example #2:>.c5(1) # see the 1st explanation

";.zchapter5(i)}

.n5chapter<-20
.zchapter5<-function(i){
    if(i==0){
       print(.c5)
    }else{
      .printEachQ(5,i,.n5chapter)
    }
}
.c5<-.chapter5

.C5EXPLAIN1<-"Simple for loop 
///////////////////////////
# Example #1:

  for(i in 1:3) print(i)

# Example #2:

  n<-1:10
  for(j in n) print(j)

# Example #3:
  tickers<-c(\"ibm\",\"c\",\"wmt\")
  for(ticker in tickers)print(ticker)

///////////////////////////
"
.C5EXPLAIN2<-"Double for loops
///////////////////////////

  for(i in 1:100){

     for(j in 1:30){

          # your code here 
    }

  }

///////////////////////////
"
.C5EXPLAIN3<-"while loop
///////////////////////////

   i<-1
   whle (i<100){
       x<-i+3
       print(x)
       i<-i+1
   }

///////////////////////////
"
.C5EXPLAIN4<-"infinitive loop
///////////////////////////

   i<-1
   whle (i<100){
       x<-i+3
       print(x)
   }

///////////////////////////
"
.C5EXPLAIN5<-"How to stop an infinitive loop
///////////////////////////

  Click the red Stop icon on the menu bar

///////////////////////////
"

.C5EXPLAIN6<-"add break clause
///////////////////////////

   i<-1
   while (2==2){
       i<-i+3
       print(i)
       if(i>29) 
         break
   }

///////////////////////////
"

.C5EXPLAIN7<-"Length of a vector and dimension of a matrix 
///////////////////////////

   x<-seq(1,50,0.123)
   n<-length(x)

   dim() function is for matrices

///////////////////////////
"

.C5EXPLAIN8<-"Loops vs. matrix manipulation 
///////////////////////////
Sometimes, matrix manipulation could save us lots of time. 

For example, assume that we have a price vector, such as
  p<-c(100,102,99,120,98,120)

Assume that the price vector is sorted from the oldest to newest. 
  In other words, the first return is (102-100)/100=0.02

Method I: we use a loop
          n<-length(p)
          for(i in 1:(n-1)){
             r[i]<-p[i+1]/p[i]-1
          }

Method II: use a matrix manipulation 
           r2<-p[2:n]/p[1:(n-1)]-1

///////////////////////////
"
.C5EXPLAIN9<-"Complex examples
///////////////////////////
Retrieve the data set of stockMonthly
  Write two loops to estimate annual risk for each stock

  > .search(\"stockMont\")
           DIR                       NAME
   691 data_sas stockmonthly.sas7bdat     
   692 data_sas stockmonthly65_89.sas7bdat

> .download2cTemp(691)
   # File/data set called  stockmonthly.sas7bdat  was successfully downloaded 
   # Your saved file/data is ==>c:/temp/stockmonthly.sas7bdat 
> 
> library(haven)
> x<-read_sas(\"c:/temp/stockmonthly.sas7bdat\")
> head(x)
# A tibble: 6 x 5
  SYMBOL ADJUSTED DATE           n     RET
  <chr>     <dbl> <date>     <dbl>   <dbl>
1 A          22.8 2008-01-31    20 -0.0672
2 A          20.6 2008-02-29    20 -0.0960
3 A          20.1 2008-03-31    20 -0.0255
4 A          20.3 2008-04-30    22  0.0127
5 A          25.2 2008-05-30    21  0.238 
6 A          23.9 2008-06-30    21 -0.0495

> y<-data.frame(x)
> head(y)
  SYMBOL ADJUSTED       DATE  n         RET
1      A 22.80688 2008-01-31 20 -0.06721765
2      A 20.61780 2008-02-29 20 -0.09598336
3      A 20.09242 2008-03-31 20 -0.02548201
4      A 20.34838 2008-04-30 22  0.01273913
5      A 25.18456 2008-05-30 21  0.23766918
6      A 23.93847 2008-06-30 21 -0.04947825
> dim(y)
   [1] 58681     5

///////////////////////////
"
.C5EXPLAIN10<-"if-stop() condition 
/////////////////////////////////

  r<- -0.1

 if(r<0) stop('Rate is less than zero!')

/////////////////////////////////
"
.C5EXPLAIN11<-"if() statement 
/////////////////////////////////

   if(npv>0) print('accept the project')

   if(condition){
  
       # your code here 

   }

/////////////////////////////////
"
.C5EXPLAIN12<-"ifelse() function 
/////////////////////////////////  

 This is quite similar to the Excel if() condition

   ifelse(condition, true, false)

  ifelse(a>0, \"positive\", \"not-positive\")

/////////////////////////////////
"
.C5EXPLAIN13<-"if-else 
/////////////////////////////////

  if(condition){

  }else{

  }

/////////////////////////////////
"
.C5EXPLAIN14<-"if else if() 
/////////////////////////////////

  if(condition1){

  }else if(condition2){

  }else if(condition3){

  }else if(condition4){

  }else{

  }

/////////////////////////////////
"
.C5EXPLAIN15<-"logic OR
/////////////////////////////////
We use | for logic or

 if(x>0 | y>0) print('at least one is positive')

/////////////////////////////////
"
.C5EXPLAIN16<-"Logic and 
/////////////////////////////////

  We use & for logic or

     if(x>0 & y>0) print('Both are positive')

/////////////////////////////////
"

.C5EXPLAIN17<-" (a and b) or (d and e)
/////////////////////////////////
a<-T
b<-T
d<-F
e<-T

     if((a==T & b==T) | (d==T & e==T)){
         print('(a and b) or (d and e)')
     }else{
         print('not correct')
     }

/////////////////////////////////
"

.C5EXPLAIN18<-"Embedded conditions 
/////////////////////////////////
   > a<-90
   > if(a) print('haha')
   [1] \"haha\"


   > a<-0
   > if(a) print('haha')


   > a<--9
   > if(a) print('haha')
     [1] \"haha\"
/////////////////////////////////
"


.C5EXPLAIN19<-"Videos
///////////////////////////
 Hutson,Gary, 2017, R Programming - For Loops
    (v11k,s673,t12:18)
    https://www.youtube.com/watch?v=50Il-XNEZng

 Math Partner, 2017, R Basics 6 - While and For Loops
    (v5k,s4k,t12:10)
    https://www.youtube.com/watch?v=LNpg8jgGex4

 Webster, Richard, 2015, For loops
    (v77k,s5k,t11:33)
    https://www.youtube.com/watch?v=h987LWDvqlQ

 DataCamp, 2015, R Tutorial - How To Use Conditional Statements in R
    (v42k,s84k,t4:26)
    https://www.youtube.com/watch?v=qvSKipqzg3U

 R-programming Library, 2018, ifelse() function in R
    (v4k,s675,t3:26)
    https://www.youtube.com/watch?v=FG_38X1ZMoc

 Maths Partner, 2017, R Basics 8 - If Statements with Multiple Conditions
    (v14k,s4k,t10:25)
    https://www.youtube.com/watch?v=a2vaD_EqTNE
///////////////////////////
"

.C5EXPLAIN20<-"Links
///////////////////////////
 Carpentries, 2018, Loops in R
    https://swcarpentry.github.io/r-novice-inflammation/15-supp-loops-in-depth/

 Fanara,Carlo, 2018, A Tutorial on Loops in R - Usage and Alternatives
    https://www.datacamp.com/tutorial/tutorial-on-loops-in-r

 R if else Statement
      https://www.datamentor.io/r-programming/if-else-statement/

  Vries, Andrie de and Joris Meys,How to use R if condition 
      https://www.dummies.com/programming/r/how-to-use-if-statements-in-r/
///////////////////////////
"