R loop and if else

Question

I would like to assign variable 'ax' with a value in looping. My code is :

 ax<-0
 for (i in i:4){
 if(i%%4==1)
 {
    ax[i]<-"one"
 }
 else if(i%%4==2)
 {
     ax[i]<-"two"
 }
 else if(i%%4==3)
 {
     ax[i]<-"three"
 }
else
 {
     ax[i]<-"four"
 }

}

I expect I got ax[1], ax[2], ax[3], and ax[4] ,

"one"    "two"     "three"     "four"

but I got :

"0"    NA     NA     "four"

This is just a try, a real code are much more longer. but the 0nly main problem is about assigning value to respective array variable. Anything wrong with this?

here I add the real code

#library(sqldf)
n = 4
a=0
b=0
c=0
d=0
e=0
f=0
g=0
h=0

Sui_Q1_STS<-0
Sui_Q1_TS<-0
Sui_Q1_S<-0
Sui_Q1_SS<-0
Sui_Q2_STS<-0
Sui_Q2_TS<-0
Sui_Q2_S<-0
Sui_Q2_SS<-0
for (i in 1:n){

 if(i%%4==1)
 {
a<-sqldf("SELECT count([X.0]) from testes where [X.0]='Sangat Tidak Setuju' and (StartDate like '%11/05/2015 00:%' or StartDate like '%11/05/2015 01:%' or StartDate like '%11/05/2015 02:%' or StartDate like '%11/05/2015 03:%' or StartDate like '%11/05/2015 04:%' or StartDate like '%11/05/2015 05:%' or StartDate like '%11/05/2015 06:00%')")
#b c d e f g and h are also sqldf
Sui_Q1_STS[i]<-as.numeric(a)
Sui_Q1_TS[i]<-as.numeric(b)
Sui_Q1_S[i]<-as.numeric(c)
Sui_Q1_SS[i]<-as.numeric(d)
Sui_Q2_STS[i]<-as.numeric(e)
Sui_Q2_TS[i]<-as.numeric(f)
Sui_Q2_S[i]<-as.numeric(g)
Sui_Q2_SS[i]<-as.numeric(h)


Sui_Q1<-list()
Sui_Q1[[i]]<-cbind(Sui_Q1_STS[i],Sui_Q1_TS[i],Sui_Q1_S[i],Sui_Q1_SS[i])
Sui_Q2<-list()
Sui_Q2[[i]]<-cbind(Sui_Q2_STS[i],Sui_Q2_TS[i],Sui_Q2_S[i],Sui_Q2_SS[i])
Total[i]<-Sui_Q1[[i]][,1]+Sui_Q1[[i]][,2]+Sui_Q1[[i]][,3]+Sui_Q1[[i]][,4]
}
   else if(i%%4==2){

  #only different in SQL
   }
   else if(i%%4==3){

  #only different in SQL
}
   else if(i%%4==0){

   #only different in SQL
}

}

and I got :

> Sui_Q1
[[1]]
NULL

[[2]]
NULL

[[3]]
NULL

[[4]]
     [,1] [,2] [,3] [,4]
[1,]    0    0    4    4

You don't need a loop. c("four", "one", "two", "three")[as.numeric(factor((v1%%4==1) + 2*(v1%%4==2) + 4*(v1%%4==3)))] where v1 <- sample(1:4, 10, replace=TRUE) — akrun
– akrun, Commented May 2, 2016 at 3:14
@akrun I need it. the looping is not just 4 actually. I will do like 50-100++ looping — Elbert
– Elbert, Commented May 2, 2016 at 3:19
The above code has a typo. The for statement should be "1:4" and not "i:4". In any case see akrun's suggestion for much better R coding style. — Dave2e
– Dave2e, Commented May 2, 2016 at 3:19

akrun · Accepted Answer · 2016-05-02 03:24:37Z

3

If we need to convert the numbers to english words

library(english)
english(v1)
#[1] two   one   three three three four  two   four  four  two

Or using base R without any loop

c("four", "one", "two", "three")[as.numeric(factor((v1%%4==1) + 
             2*(v1%%4==2) + 4*(v1%%4==3)))]
#[1] "two"   "one"   "three" "three" "three" "four"  "two"   "four"  "four"  "two"

If we really need a loop

 ax <- numeric(4)
 for(i in 1:4){
  if(i%%4 ==1){
  ax[i] <- "one"
  } else if (i%%4 ==2){
 ax[i] <- "two"
 }else if (i%%4 ==3){
  ax[i] <- "three"
 } else {
  ax[i] <- "four"
  }
 }

ax
#[1] "one"   "two"   "three" "four"

data

set.seed(24)
v1 <- sample(1:4, 10, replace=TRUE)

edited May 2, 2016 at 3:24

answered May 2, 2016 at 3:17

akrun

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3 Comments

Elbert Over a year ago

I did post the new question with reproducible code. here : stackoverflow.com/questions/36974742/… please check

Elbert Over a year ago

I got the answer. my fault to assign Sui_Q1 as a list more than once.

Elbert Over a year ago

and ur way to do the looping can be implemented. thank you

Matthew Lundberg · Accepted Answer · 2016-05-02 03:25:49Z

2

This very simple expression does what you want:

i <- 1:4
c("four", "one", "two", "three")[i %% 4 + 1]
## [1] "one"   "two"   "three" "four"

answered May 2, 2016 at 3:25

Matthew Lundberg

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