| How does REFORM work in PV-Wave [message #18096] |
Tue, 30 November 1999 00:00  |
jeyadev
Messages: 78
Registered: February 1995
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Member |
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I have a question about the way reform works on 3d arrays.
First, the specific problem. I have a data file that has 8 columns and
56 rows. Each column corresponds to an independent variable. The
The 56 rows correspond to an 8 x 7 array of points on a plane. What I
would like to do is to read the data file and then make a new 3d array
so that each plane of this 3d array corresponds to one of the independent
variables (so that there are 8 separate 8 x 7 planes).
After some experimentation I found that the solution was
newdata = reform(data, 8, 8, 7)
But, I do not understand why this works. In fact, I find it quite
counter intuitive and I do not understand why the 'plane' index
should be the first one (more below). The fact that there is a
degeneracy here made my experimentation easier! There are only 3
possibilities, instead of 6. But, that raises the more interesting
question. Also, I understand that the first index of newdata
identifies the *plane* for each variable and I can do, for example,
surface, reform(newdata(1,*,*))
to see how the second variable varies over the plane. Now,
if I had N variables on a grid with C columns and R rows
and the data file was in the format
r1 c1 v1 v2 v3 ... vN
r2 c1 v1 v2 v3 ... vN
......
......
R c1 v1 v2 v3 ... vN
r1 c2 ....
r2 c2 ....
etc. In the above, you can ignore the first two columns -- they are
there just to show the order. The actual data and just C x R rows
of N elements each.
what would be the reform command be? (With that I should be able
to figure out the answer for what it should be in the row and column
orders were reversed in the original data file!)
I guess what I am missing is the *order* in which elements are stored.
I think that PV-Wave stores 2d arrays in the 'row' format (first index
varies fastest), but what about higher dimensional arrays?
thanks
--
Surendar Jeyadev jeyadev@wrc.xerox.com
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