If-Else logic flow - if-statement

Question

Can anyone explain to me why the distribution for this code:
InfectionHistory <- rep(1,100)
for(x in 1:99)
{
r <- runif(1)
print(r)
if(InfectionHistory[x]==1)
{
if(r < 0.04)
{
InfectionHistory[x+1] <- 2
}
else
{
InfectionHistory[x+1] <- InfectionHistory[x]
}
}
if(InfectionHistory[x]==2)
{
if(r < 0.11)
{
InfectionHistory[x+1] <- 1
}
else
{
InfectionHistory[x+1] <- InfectionHistory[x]
}
}
}
plot(InfectionHistory, xlab = "Day", ylab = "State", main = "Patient Status per Day", type = "o")
is different from this code:
InfectionHistory <- rep(1,100)
for(x in 1:99)
{
r <- runif(1)
print(r)
if((InfectionHistory[x]==1)&&(r < 0.04))
{
InfectionHistory[x+1] <- 2
}
if((InfectionHistory[x]==2)&&(r < 0.11))
{
InfectionHistory[x+1] <- 1
}
}
plot(InfectionHistory, xlab = "Day", ylab = "State", main = "Patient Status per Day", type = "o")
I feel like it has to do with the logic of if-else statements. The objective of the code is to simulate an infection model along the lines of a Markov chain

Answer 1

The first example contains if else pairs nested within if statements.
The second example contains if statements with compound conditions.
Upon cursory review, it looks like each example should do the same thing. This code serves as an example that nested if statements can be rewritten as if statements with compound conditions.
For example, in example 1, when we get to this line of code:
if(r < 0.04)
{
InfectionHistory[x+1] <- 2
}
We already know that
InfectionHistory[x]==1
has returned true, or else we wouldn't be within the body of the if that checked this condition.
In the second example, this is simply rewritten as:
if((InfectionHistory[x]==1)&&(r < 0.04))
{
InfectionHistory[x+1] <- 2
}
EDIT: Looking at it again, the second example doesn't seem to have a case for handling:
else
{
InfectionHistory[x+1] <- InfectionHistory[x]
}
This bit of code is repeated in the first example. It is paired with both nested if statements. The second example could easily be rewritten to handle this however with a simple if else if else structure. For example:
if((InfectionHistory[x]==1)&&(r < 0.04))
{
InfectionHistory[x+1] <- 2
}
else if((InfectionHistory[x]==2)&&(r < 0.11))
{
InfectionHistory[x+1] <- 1
}
else
{
InfectionHistory[x+1] <- InfectionHistory[x]
}