Nested If statements in R

I have a function in R that evaluates several if statements within an if statement. It's returning an error message when I run it (I'm only including the sketh of the code, because the actual function is quite big):

if (X_star - x != 0){
if (w == 1){
  #stuff 
  } else {
    #stuff 
  if (X_star == 1){
    #Stuff
    } else {
      #Stuff
      }
  #Stuff
  }
Y = something   
if (Y == 1){
  #Stuff
  } else {
    #Stuff
  }
} else {
  if (Xmax - x !=0){
    Y = something else       
    if (Y == 1){
      #Stuff
      } else {
        #Stuff
      }
    } else {
      #Stuff
    }
  }

Error in if (X_star - x != 0) { : missing value where TRUE/FALSE needed.

I read some other posts where people seemed to have the same problem, but I couldn't find a definitive answer. I've stared at it for some time but can't find what is wrong with it. This function is located within a for loop, so I can't really use the vectorized ifelse. I'd appreciate any help.

Cheers,

Napo