Declarations
Typically, compiled languages require that you declare variables; that is, warn the interpreter/compiler of the variables’ existence before using them. This is the case in our earlier C example:
int x; int y[3];
As with most scripting languages (such as Python and Perl), you do not declare variables in R. For instance, consider this code:
z <- 3
This code, with no previous reference to z
, is perfectly legal (and commonplace).
However, if you reference specific elements of a vector, you must warn R. For instance, say we wish y
to be a two-component vector with values 5 and 12. The following will not work:
> y[1] <- 5 > y[2] <- 12
Instead, you must create y
first, for instance this way:
> y <- vector(length=2) > y[1] <- 5 > y[2] <- 12
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