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Re: Referencing elements of array expressions [message #3521 is a reply to message #3513]

Sun, 05 February 1995 18:10

steinhh
Messages: 260
Registered: June 1994

Senior Member

In article <3guag9$nqn@marsupial.jpl.nasa.gov>, "Evan F. Fishbein" <eff@tugh.jpl.nasa.gov> writes:
|>
|> A simple question -- Is is possible to reference elements
|> of array expressions. For example, can the last two lines of
|> the following code:
|>
|> x=findgen(40)/10.0
|> y=cos(2.0*!pi*x)
|> i=where(abs(y) lt 1.0e-5)
|> i=i(0:1)+[-1,1]
|>
|> be combined into one line by accessing the first
|> element of the expression "where(abs(y) lt 1.0e-5)"
|> without placing the vector result in a dumy array variable?
|>

Yes, it's possible:

i = (where(abs(y) lt 1.0e-5))(0:1)+[-1,1]

and in general, you can reference elements of arrays in expressions
by adding parentheses around the array expression, and then the index
in another pair of parentheses:

sub_array = (my_arrayfunc(0.5))(0:5)

I wouldn't recommend it in your example, though, because WHERE might
return a scalar long if no elements match the test, but I often use
it with e.g. N_DIMENSIONS = (SIZE(a))(0)

Stein Vidar

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		Re: Referencing elements of array expressions By: velt on Mon, 06 February 1995 08:18
		Re: Referencing elements of array expressions By: steinhh on Sun, 05 February 1995 18:10

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