R, a powerful statistical programming language, stands out for its expressive syntax and flexibility. As an expression language, it offers a straightforward way to manipulate and analyze data. However, users need to be aware of certain characteristics, such as its case sensitivity, symbol set variations based on locale, and the structure of elementary commands.
Case Sensitivity in R
One notable feature of R is its case sensitivity. Much like many UNIX-based packages, R treats uppercase and lowercase letters as distinct symbols. For instance, 'A' and 'a' would be recognized as separate variables. This case sensitivity can catch users off guard, and it's crucial to pay attention to letter casing when working with R to avoid unintended errors.
Symbol Set Variations
The set of symbols allowed in R names is contingent on the operating system and country in which R is executed, technically determined by the locale in use. Generally, alphanumeric symbols, including accented letters in some countries, are permitted. Additionally, the use of period ('.') and underscore ('_') is allowed. However, there are constraints, such as names needing to start with a period or a letter, and if starting with a period, the second character must not be a digit. Thankfully, R is relatively permissive, and names can be of unlimited length.
Elementary Commands and Expressions
In R, elementary commands take the form of either expressions or assignments. When an expression is used as a command, it is evaluated, printed (unless specified otherwise), and the value is discarded. On the other hand, an assignment not only evaluates an expression but also assigns the result to a variable. It's important to note that the result of an assignment is not automatically printed.
Command Structure and Separation
Commands in R can be separated by a semi-colon (';') or a newline character. Moreover, elementary commands can be grouped into compound expressions using curly braces ('{' and '}'). This allows for the organization of code blocks and enhances readability.
Comments and Continuation
Adding comments to your R code is essential for documentation. Comments in R start with a hashmark ('#'), and anything following it on the same line is treated as a comment. This helps improve code clarity and understanding.
In cases where a command spans multiple lines, R uses a continuation prompt to indicate that the command is not complete. By default, the continuation prompt is '+', but users can customize it according to their preferences. It is crucial to be aware of continuation prompts and appropriately structure multi-line commands to avoid syntax errors.
Command Line Limitations
When working with R at the console, it's essential to be mindful of command line limitations. The input for a command is restricted to approximately 4095 bytes, not characters. Users should be aware of these constraints, especially when dealing with large datasets or complex operations.
