REVERSE Function

Standard Library function that reverses a vector or array for a given dimension.

result = REVERSE(array, [dimension])

array The vector or array to be reversed.

dimension (optional) The dimension of array to be reversed, such as the rows or columns. (Default: reverse rows, the first dimension).

result The vector or array that has been reversed.

None.

REVERSE is helpful in a variety of applications; one example is its use in obtaining perfectly symmetrical figures, such as an hourglass, by simply creating a portion of the needed figure and then making a reverse image for the rest.

This example exhibits the result of applying REVERSE to a 4-by-3 integer array.

a = INDGEN(4, 3)

; Create a 4-by-3 integer array. Each element has a value equal to its
; one-dimensional subscript.

PRINT, a

0       1       2       3
4       5       6       7
8       9      10      11

PRINT, REVERSE(a)

  3       2       1       0
  7       6       5       4
11      10       9       8

; Reverse the rows of a.

PRINT, REVERSE(a, 2)

8       9      10      11
4       5       6       7
0       1       2       3

; Reverse the columns of a.

PRINT, REVERSE(REVERSE(a), 2)

11      10       9       8
  7       6       5       4
  3       2       1       0

; Reverse the columns and rows of a.

The following commands first display the image contained in the scientist3.dat file, and then rotate and redisplay it:

image1 = BYTARR(250, 200)
OPENR, 1, !Data_dir + 'scientist3.dat'
READU, 1, image1
TV, image1, 0
TV, REVERSE(image1), 1

ROTATE