CODEWITHSUNDEEP
rif-statement
MasterJedi
MasterJedi

Reputation: 1638

if - else if - else statement and brackets

I understand the usual way to write an "if - else if" statement is as follow:

if (2==1) {
  print("1")
} else if (2==2) {
  print("2")
} else {
  print("3")
}

or 

if (2==1) {print("1") 
} else if (2==2) {print("2")
} else print("3")

On the contrary, If I write in this way

if (2==1) {
  print("1")
} 
else if (2==2) {
  print("2")
}
else (print("3"))

or this way:

if (2==1) print("1") 
else if (2==2) print("2")
else print("3")

the statement does NOT work. Can you explain me why } must precede else or else if in the same line? Are there any other way of writing the if-else if-else statement in R, especially without brackets?

Upvotes: 37

Views: 120406

Answers (4)

Talha Rasool
Talha Rasool

Reputation: 1152

ifelse has tree parametes, first conditon, second true result and last false result. 

y_pred = ifelse(prob_predict > 0.5,1,0)

Upvotes: 0

singuyenmai
singuyenmai

Reputation: 33

As hrbrmstr has mentioned:

When the initial if is followed by a compound expression (indicated by the {} pair) the parser by default is going to expect the expression followed by else to be compound as well. The only defined use of else is with compound expressions.

In the statement if(cond) cons.expr else alt.expr, the else needs to be put after and in same line with the end `cons.expr' compound.

So if you want to have your code a better look without brackets, apply this way:

if (2==1) print("1") else 
   if (2==2) print("2") else 
      print("3")

Upvotes: 2

Berry Boessenkool
Berry Boessenkool

Reputation: 1538

R reads these commands line by line, so it thinks you're done after executing the expression after the if statement. Remember, you can use if without adding else.

Your third example will work in a function, because the whole function is defined before being executed, so R knows it wasn't done yet (after if() do).

Upvotes: 41

Honey
Honey

Reputation: 141

In R, also we have ifelse() function:

ifelse(1 < 0, "hello", "hi")

Output:

# [1] "hi"

Upvotes: 14

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