Determining the Size/Type of an Array

The SIZE function returns a vector that contains information indicating the size and type of the parameter. The returned vector is always of longword type.

The first element is equal to the number of dimensions of the parameter and is zero if the parameter is a scalar.

The next elements contain the size of each dimension.

After the dimension sizes, the last two elements indicate the data type and the total number of elements, respectively. The data type is encoded as follows:


Type Code	Data Type
0	Undefined
1	Byte
2	Integer (16-bit)
3	Longword integer (32-bit)
4	Floating point
5	Double-precision floating
6	Complex floating
7	String
8	Structure
9	Double-precision complex floating
10	Pointer
11	Object reference
12	Unsigned integer (16-bit)
13	Unsigned longword integer (32-bit)
14	64-bit integer
15	Unsigned 64-bit integer

The data type can also be returned by setting the TYPE keyword to SIZE. In this case, the return value of the SIZE function is the data type code of the given expression.

Examples

Example 1


Element	Value	Description
S₀	3	Three dimensions
S₁	3	First dimension
S₂	4	Second dimension
S₃	5	Third dimension
S₄	2	Integer type
S₅	60	Number of elements = 345

The following code segment checks to see if the variable arr is two-dimensional and extracts the dimensions:

;Create a variable. 
arr = [[1,2,3],[4,5,6]] 
 
;Get size vector. 
S = SIZE(arr) 
 
;Check if two dimensional. 
IF S[0] NE 2 THEN $ 
   ;Print error message. 
   MESSAGE, 'Variable a is not two dimensional.' 
 
;Get number of columns and rows. 
NX = S[1] & NY = S[2] 
 
PRINT, 'Array is ', NX, ' columns by ', NY, ' rows.'

Example 2

The following example illustrates two ways in which to determine the type code of the input expression.

The first method requires you to access the correct element of the array returned by the SIZE function (the second to last element). For example:

array = [[1,2,3], [4,5,6], [7,8,9]] 
 
sz = SIZE(array) 
type = sz[3] 
 
;A more flexible method: 
sz = SIZE(array) 
n = N_ELEMENTS(sz) 
type = sz[n-2]

The second method involves using the TYPE keyword to SIZE. In this case, the value returned by the SIZE function contains only the type code of the input expression: