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Re: How to use pointers instead of arrays [message #33125]

Tue, 10 December 2002 10:51

MKatz843
Messages: 98
Registered: March 2002

Member

If your arrays are reasonably sized, there's an even easier way to
appean columns or rows to an array. OK, so it's not the best method
for memory management or speed, but for many applications,
it works just fine.

In IDL you can do this:

a = [1,2,3]
b = [a, 5]
print, b
1 2 3 5
or
c = [5, a]
print, c
5 1 2 3

So in 2-D you can do this
a = indgen(3,3)
print, a
0 1 2
3 4 5
6 7 8
b = [[a],[9,9,9]] ; append a row to the end
print, b
0 1 2
3 4 5
6 7 8
9 9 9
c = [a,transpose([9,9,9])] ; turn a vector into a column and append
print, c
0 1 2 9
3 4 5 9
6 7 8 9
The number of brackets is related to how many dimensions you're
working with. You can do all of this in 3, 4, or more dimensions
if you're willing to keep track of the brackets.

Of course, you can replace the original variable with the same command:
a = [a, something].

For memory usage, it's not the best method; but for coding elegance,
it's quite compact. IDL is great for on-the-fly variable definitions.

I hope this helps,
M. Katz

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[Message index]

		Re: How to use pointers instead of arrays By: MKatz843 on Tue, 10 December 2002 10:51
		Re: How to use pointers instead of arrays By: JD Smith on Mon, 09 December 2002 09:51
		Re: How to use pointers instead of arrays By: David Fanning on Mon, 09 December 2002 06:56
		Re: How to use pointers instead of arrays By: paul wisehart on Mon, 09 December 2002 06:39

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