| VECTOR_FIELD trouble [message #49859] |
Tue, 22 August 2006 04:12 |
Jo Klein
Messages: 54
Registered: January 2006
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Member |
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Dear IDL wizards,
Has anyone got experience with the use of VECTOR_FIELD? The data I have
is quite simple: It's a volume of vectors, where for each spatial
position of a 3D regular grid I've got x, y and z as the projections of
a unit-length vector centred on those grid locations. It's volume data
from diffusion tensor MRI, and the vectors describe apparent diffusion
directions at any given point in the object studied (a brain, in this
case). So, to visualise the vectors, I browsed the docs and thought
VECTOR_FIELD should do the job, but I can't figure out how to use it.
One slice extracted from the data looks like this (z dimension of the
vectors dropped):
IDL> help,myslice
MYSLICE FLOAT = Array[2, 128, 104]
IDL> print,myslice[*,60:62,50]
-0.393992 0.305778
-0.353878 0.368543
-0.505301 0.394556
I set up my vectors like this:
IDL> vector_field,myslice,outverts,outconn
IDL> plots,outverts
.. and the result is a window with just a wobbly looking vertical line,
instead of lots of little vectors on a rectangular region.
IDL> print,outverts[*,10000:10002]
8.00000 39.0000
8.00000 39.0000
9.00000 39.0000
I suppose I'm misinterpreting how IDL would like my input data to be
formatted, but as there are no examples in the VECTOR_FIELD docs, I'm a
bit at a loss here.
I'd appreciate any help you can give.
Thanks a lot everyone,
Jo
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