Question

Can an if statement have more than one then statements?

# this works

a <- c(1,2,3,4,5,6,7,8,9,10)
b <- c(4,3,5,2,8,9,1,2,2,4)
c <- c(9,9,9,5,5,5,2,2,2,1)
for(i in 1:10) { if(c[i]==2) a[i]= 100; if(c[i]==2) b[i]= -99  }


# this does not work

d <- c(1,2,3,4,5,6,7,8,9,10)
e <- c(4,3,5,2,8,9,1,2,2,4)
f <- c(9,9,9,5,5,5,2,2,2,1)
for(i in 1:10) { if(f[i]==2) (d[i]= 100 & e[i]= -99)  }

Answer 1

You’re probably confusing if-expressions (a.k.a. ternary operators) with if-statements. In the latter, you usually have a brace-enclosed block of statements, which are delimited by semicolons or newlines:

R> for(i in 1:10) if(f[i]==2) { d[i]= 100; e[i]= -99 }
R> d
 [1]   1   2   3   4   5   6 100 100 100  10
R> e
 [1]   4   3   5   2   8   9 -99 -99 -99   4

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Also, here is a somewhat faster equivalent:

a[which(c==2)] = 100
b[which(c==2)] = -99