“You can have data without information, but you cannot have information without data” — Daniel Keys Moran
Almost all programming languages explicitly include the notion of data type, though different languages may use different terminology. That means when programming, the variables generally have a specific type, and they should be selected the appropriate type according to what you want to use the variable for.
Common data types include:
- double or floating-point number
- logical or boolean
- NULL and/or NA
Data types are used within type systems, which offer various ways of defining, implementing and using them. Different type systems ensure varying degrees of type safety.
int is short for “integer”, which means whole numbers. It is used to specify that the variable contains only whole numbers. For example, 3 is an integer but 3.25 is not an integer. The range goes from -2,147,483,648 to 2,147,483,647.
Double or Floating-point number
float is short for “floating-point number”, which is a fractional number, eg, 3.25907. This can be a number between roughly 1.5 x 10^45 to 3.4 10^38, in floating point format.
Note: Watch your decimal separator! The decimal separator is a symbol used to separate the integer part from the fractional part of a number written in decimal form. Different countries officially designate different symbols for use as the separator. The choice of symbol also affects the choice of symbol for the thousands separator used in digit grouping.
Currently there are three ways to group the number ten thousand with digit group separators.
|10 000,00||Space, the internationally recommended thousands separator|
|10.000,00||Period (spoken as point), the thousands separator in many non-English speaking countries.|
|10,000.00||Comma, the thousands separator used in most English speaking countries.|
The first one is not suitable for data entry because of the space character.
With the second and third selection, it is very important to pay attention to the decimal separator with which the original data is saved. In Europe the point is preferred for thousands and the comma for decimals. In English-speaking countries, the comma is selected for thousands and the point is being used for decimals. Accordingly, care must be taken when importing the data.
More information on this in Chapter 6: In- and Output of Data
characters basically behave like words. They can be stringed together, they can be compared, but they can’t be used for calculations.
Examples of characters include letters, numerical digits, common punctuation marks (such as “.” or “-“), and whitespace. The concept also includes control characters, which do not correspond to visible symbols but rather to instructions to format or process the text. Examples of control characters include carriage return or tab, as well as instructions to printers or other devices that display or otherwise process text.
Characters are typically combined into strings. A string is a sequence of characters, e.g. “Hello World.” It is used to represent text rather than numbers. It is comprised of a set of characters that can also contain spaces and numbers. For example, the word “hamburger” and the phrase “I ate 3 hamburgers” are both strings, consisting of characters.
Logical or boolean
Logical values or boolean values can only contain either the value true or false.
NULL or NA
Both are used to represent missing or undefined values.
It is common for programming languages to have a NULL value. What often leads to confusion is the fact NULL can have two distinct meanings. In the first, NULL is used to represent missing or undefined values. In the second case, NULL is the logical representation a statement that is neither TRUE nor FALSE. This indeterminacy is the basis for ternary logic.
Ternary logics are examples of multivalent logics. This means that instead of two truth values there are three. Instead of only “true” (1) and “false” (0) there are also “unknown”, “undetermined” or “don’t care”.
The R language has two closely related NULL-like values, NA and NULL. Both are fully supported in the language by core functions (e.g, is.na, is.null, as.null, etc.). And, while NA is used exclusively in the logical sense, both are used to represent missing or undefined values.
|integer||1; 15 ; 1984297|
|float||1.15 ; 1007.28 ; 0.0001|
|character||© ; H ; π ; A; B; C|
|string||“Hello World” ; “Ursus maritimus” ; “black”|
|boolean||true ; false|
Take the test, to check if you understand everything correctly:
Let’s move on…