The document discusses various principles and best practices for writing readable code in R, including using <- for assignment, writing logical operations to clearly show comparisons, avoiding overly long parameter passing, and setting default parameter values. It provides examples of clearer and more intuitive ways to write common code structures like conditional statements, assignments, and function definitions. The overall goal is to write code that is easy for both the original author and others to understand at a later time.

1. Code Readability in R
Kim Man Lui, PhD
Code readability is actually for more
yourself than others.
Note: R guys generally use “<-” in R;
however, many developers have used “=“ in
programming for decades.
Does this really matter? (see #8)

2. #1 Which one is precise?
if (0==colCon) {
pv=0
} else {
pv=(colCon * 4.5 - 10 )/100
}
pv = if (0==colCon) 0 else (colCon * 4.5 - 10 )/100
A
B

3. #2 Which is easier to understand?
pointVal = if (0==colConDex) 3 else 6
bheadtmp = bhead + pointVal
bheadtmp = bhead +
if (0==colConDex) 3 else 6
A
B

4. #3 When B is better than A?
coeff[[1]][[1]]= coeff[[1]][[2]]=rep(0,20)
coeff[[1]][[1]][4]=1
coeff[[1]][[1]][6]=1
… … …
coeff[[1]][[1]]=c(0,0,0,1,0, 1,0,0,0,0, 0,0,0,0,0, 0,0,0,0,0)
coeff[[1]][[2]]=c(0,0,0,0,0, 0,0,1,0,0, 0,0,0,0,0, 0,0,0,0,0)
A
B

5. #4 Which is simpler?
d100=performanceCheck(100)
d50 =performanceCheck(50)
d21 =performanceCheck(21)
d14 =performanceCheck(14)
… … … … …
perf=sapply( data.frame(d100=100, d50=50, d21=21, d14=14),
performanceCheck)
A
B

6. #5 Power of Style
A
B

7. #6 Rank the following statements!
A
B
C

8. A
B
#7 Which is easier to understand?

9. #8 Which one is incorrect?
demo=function ( x , y=2) {return (x+y)}
demo=function ( x , y <- 2) {return (x+y)}
Y <- 2
Y = 2A
B
C
D

10. #9 Which one is intuitive?
s=subset(s, (as.Date(today)-30) <=
time(s) & time(s)<=today & 0<s[,5])
s=subset(s, time(s)>=(as.Date(today)-30)
& time(s)<=today & s[,5]>0)
A
B
General Principle :
when assigning a number to a variable, write as var=1
when doing logical operations, try to write as 1==var
This way helps our eyes to judge assignment or comparison quickly

11. #10 Should we avoid a long way to passing parameters?
fa=function(x1) {
a1=mean(x1) ; return (a1) }
fb=function(x2,y2, isLog=TRUE) {
a2=x2-y2 ; b2=fc(a2, isLog=isLog) ;
return (b2) }
fc=function(x3, isLog=TRUE) {
a3=x3*x3; b3=fd(a3, isLog=isLog)
return (b3) }
fd=function(x4, isLog=TRUE) {
a4= sum(sqrt(x4))
if (isLog==TRUE) print(paste(x4))
return (a4) }
dat=c(2,3,4,5)
fb(dat, fa(dat), isLog=FALSE)
A B
fa=function(x1) {
a1=mean(x1) ; return (a1) }
fb=function(x2,y2) {
a2=x2-y2 ; b2=fc(a2) ;
return (b2) }
fc=function(x3) {
a3=x3*x3; b3=fd(a3)
return (b3) }
fd=function(x4) {
a4= sum(sqrt(x4))
isLog=getPara(“isLog”)
if (isLog==TRUE) print(paste(x4))
return (a4) }
dat=c(2,3,4,5)
setPara(“isLog”, FALSE)
fb(dat, fa(dat))