'L'のこと

a<-1:10
a[1]
a[1.6]
a[1.6L]

を実行すると

> a<-1:10
> a[1]
[1] 1
> a[1.6]
[1] 1
> a[1.6L]
[1] 1
 警告メッセージ： 
 整数リテラル 1.6L は小数を含んでいます. 実数を利用します.  
> 

となる。
この"L"に関する記述は、マニュアルのここから抜粋して以下の通り

3.1.1 Constants

Any number typed directly at the prompt is a constant and is evaluated.

     > 1
     [1] 1
Perhaps unexpectedly, the number returned from the expression 1 is a numeric. In most cases, the difference between an integer and a numeric value will be unimportant as R will do the right thing when using the numbers. There are, however, times when we would like to explicitly create an integer value for a constant. We can do this by calling the function as.integer or using various other techniques. But perhaps the simplest approach is to qualify our constant with the suffix character `L'. For example, to create the integer value 1, we might use

     > 1L
     [1]
We can use the `L' suffix to qualify any number with the intent of making it an explicit integer. So `0x10L' creates the integer value 16 from the hexadecimal representation. The constant 1e3L gives 1000 as an integer rather than a numeric value and is equivalent to 1000L. (Note that the `L' is treated as qualifying the term 1e3 and not the 3.) If we qualify a value with `L' that is not an integer value, e.g. 1e-3L, we get a warning and the numeric value is created. A warning is also created if there is an unnecessary decimal point in the number, e.g. 1.L.

We get a syntax error when using `L' with complex numbers, e.g. 12iL gives an error.

Constants are fairly boring and to do more we need symbols.