| Re: where help [message #7900] |
Mon, 27 January 1997 00:00  |
Phil Williams
Messages: 78
Registered: April 1996
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Member |
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DUH!!!!
I should use 256 here and not 255! Became instantly obvious once the
send button was pushed and I admitted my stupidity!!! :)
Take care,
Phil
--
/*********************************************************** ********/
Phil Williams, Ph.D.
Research Instructor
Children's Hospital Medical Center "One man gathers what
Imaging Research Center another man spills..."
3333 Burnet Ave. -The Grateful Dead
Cincinnati, OH 45229
email: williams@irc.chmcc.org
URL: http://scuttle.chmcc.org/~williams/
/*********************************************************** ********/
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| Re: where help [message #7970 is a reply to message #7900] |
Wed, 29 January 1997 00:00  |
davidf
Messages: 2866
Registered: September 1996
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Senior Member |
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David Gunter <gunter@alpha1.csd.uwm.edu> writes:
> David Fanning (davidf@dfanning.com) wrote:
>
> [bunch of nonsense deleted...] :-)
> Is there a reason you wouldn't just write: row=index/s(1)? In this manner you
> will end up with the whole part automatically.
>
> And you could just as well write: col = index MOD s(1), where the MOD function
> returns the remainder of the division (index/s(1)). Of course there may be
> extra time involved (looking up the MOD function, etc) versus the above line.
Yeah, yeah, yeah. I realized all this the minute I hit the SEND key!
It's just that good ideas don't always occur to me when I am
writing programs on the fly. My method of working, to tell you
the truth, is to write some nonsense here, wait around for all
the experts to post or e-mail me the *real* answers, then write
it up as a tip on my web page like I know what I'm doing.
I figure this is about 100 times faster than looking at the
IDL documentation! :-)
Cheers!
David
-----------------------------------------------------------
David Fanning, Ph.D.
Fanning Software Consulting
2642 Bradbury Court, Fort Collins, CO 80521
Phone: 970-221-0438 Fax: 970-221-4762
E-Mail: davidf@dfanning.com
Coyote's Guide to IDL Programming: http://www.dfanning.com
-----------------------------------------------------------
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| Re: where help [message #7971 is a reply to message #7900] |
Wed, 29 January 1997 00:00 |
gunter
Messages: 13
Registered: October 1996
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Junior Member |
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David Fanning (davidf@dfanning.com) wrote:
[snip...snip]
: data = FINDGEN(12)
: data = REFORM(data, 3, 4)
: PRINT, data
: 0.00000 1.00000 2.00000
: 3.00000 4.00000 5.00000
: 6.00000 7.00000 8.00000
: 9.00000 10.0000 11.0000
: s = SIZE(data)
:
: OK, suppose I now do this:
:
: index = WHERE(data EQ 6)
:
: The WHERE function returns the 1D index into the 2D array.
:
: PRINT, index
: 6
:
: So, the number 6 is located in index 6 (the 7th number in
: the array with zero-based subscripting). What is its
: 2D subscript? Well, if I divide index by how many columns
: there are in the array, and then take the whole part of that
: number, I will know its row number. In IDL terms:
:
: row = FIX(FLOAT(index)/s(1))
: PRINT, row
: 2
Is there a reason you wouldn't just write: row=index/s(1)? In this manner you
will end up with the whole part automatically.
: To find the column number, I multiply the row number times
: the number of columns in the array, and subtract that value
: from the index. Again, in IDL terms:
:
: col = index - (row * s(1))
: PRINT, col
: 0
And you could just as well write: col = index MOD s(1), where the MOD function
returns the remainder of the division (index/s(1)). Of course there may be
extra time involved (looking up the MOD function, etc) versus the above line.
--
david gunter
http://www.mcs.anl.gov/people/gunter/
-------------------------------------
"When you are a Bear of Very Little Brain, and you Think of Things, you find
sometimes that a Thing which seemed very Thingish inside you is quite
different when it gets out into the open and has other people looking at it."
- A.A. Milne, "The House At Pooh Corner"
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| Re: where help [message #7979 is a reply to message #7900] |
Wed, 29 January 1997 00:00 |
fttji
Messages: 3
Registered: January 1997
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Junior Member |
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Phil Williams <williams@irc.chmcc.org> wrote:
> Here's what I did:
> IDL> t = where(slice eq max(slice))
> IDL> print,size(slice)
> 2 256 256 2 65536
> IDL> y = t/255
> IDL> x = t - (y*255)
Ya, you're using the wrong dimension, use 256
and I prefer x=t mod 256, though I guess yours will work.
> IDL> print,slice(y,x)
You obviously don't really want this in there!
> What is going on??? Any help would be GREATLY appreciated!
Hope this helps!
> Phil
Thomas Immel
Research Asst.
Geophysical Institute, U of Alaska Fairbanks
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| Re: where help [message #7993 is a reply to message #7900] |
Tue, 28 January 1997 00:00 |
pit
Messages: 92
Registered: January 1996
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Member |
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In article <32ED447F.1CFB@irc.chmcc.org>,
Phil Williams <williams@irc.chmcc.org> writes:
> How do I get the x,y coords from the result of where?
Maybe you find the following routine usefull. It should do what you
want for arrays of any dimension. Read the header how to use and
interpret the result.
Peter
-----------------------------
FUNCTION Prod, data
on_error, 2
produkt = 1.*data(0)
FOR i=1, n_elements(data)-1 DO $
produkt = produkt*data(i)
return, produkt
END
FUNCTION Where_n, data, cond, count
;+
; NAME:
; WHERE_N
; PURPOSE:
; Find the n-dim indices where the array DATA fullfills a given
; condition.
; CALLING SEQUENCE:
; RESULT= WHERE_N (Array condition, [,COUNT]])
; INPUTS:
; DATA : n-dim array expression as explained in the Manpage for
; where. All Constructs (like "eq 0", "GT limit" etc)
; are allowed.
; OPTIONAL INPUTS:
; COUNT : (Output) used for passing back the number of matches
; OUTPUTS:
; Result is a long array of dimension (COUNT, N) where COUNT is
; the number of zero elements in DATA and N is the dimension of
; the input array. The optional parameter COUNT holds the
; number of matches
; PROCEDURE:
; An Array expression is a byta array that is unity where the
; condition is fulfilled and zero elswhere. The where-function
; returns a 1-d array. Reformat this and return the reformated
; array.
; EXAMPLE:
; Be A an 4-dim array. The call
; Res = where_n(abs(A) LE 10)
; returns an array of the size (n_matches, 4). For example the
; 4th match element in A can be addressed as
; A(res(3,0), res(3,1), res(3,2), res(3,3)).
; MODIFICATION HISTORY:
; 20-Okt-1992 P.Suetterlin, KIS 2-d version Where2
; 29-Aug-1995 PS extended to n-dim, changed syntax to match the
; use of the IDL where-function.
;-
on_error, 2
IF n_params() EQ 0 THEN BEGIN
print, 'Use: result=where_n(data[,count]) data is n-dim array'
return, undefined
ENDIF
s = size(data)
dim = s(0)
ix = where(data EQ 1, count)
IF count EQ 0 OR s(0) EQ 1 THEN return, ix
res = intarr(count, dim)
res(*, 0) = ix MOD s(1)
FOR i=1, dim-1 DO $
res(*, i) = (ix MOD long(prod(s(1:i+1))))/prod(s(1:i))
return, res
END
--
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~
Peter "Pit" Suetterlin http://www.uni-sw.gwdg.de/~pit
Universitaets-Sternwarte Goettingen
Tel.: +49 551 39-5048 pit@uni-sw.gwdg.de
-- * -- * ...-- * -- * ...-- * -- * ...-- * -- * ...-- * -- * ...-- * --
Come and see the stars! http://www.kis.uni-freiburg.de/~ps/SFB
Sternfreunde Breisgau e.V. Tel.: +49 7641 3492
____________________________________________________________ ______________
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