[Animl-develop] Re: Vector Length Issues

[<Mar...@wa...>]

Hi Burkhard,

thanks for the clarification. This should have been in your format
documentation.

Mit freundlichen Gr=FC=DFen / Best regards

Dr. Maren Fiege
Product Manager

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             "Burkhard                                                =20
             Schaefer"                                                =20
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                                       "Mark F. Bean"                 =20
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                                       <Mar...@wa...>, "Mark F.
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                                       Vector Length Issues           =20
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Hi everybody,

I looked again at the question of the various "length" attributes in and
around the Vector element. Let's look at the various elements and what
the length attribute would mean there.

VectorSet
--------
The length attribute in the VectorSet element describes the total number
of data points in the diagram. The values (components) that make up a
data point can be retrieved by looking at the same index in all vectors.
Here's a little drawing (please forgive my poor ASCII art ;-) )

Let's say we have a UV/VIS with two vectors: Wavelength and Absorbtion.
We want to store 100 data points, so VectorSet.length is 100.

                     +----+
Wavelength  [ w1 w2 | w3 | w4 w5 ...... w100 ]
Absorbtion  [ a1 a2 | a3 | a4 a5 ...... a100 ]
                     +----+
                  3rd data point: (w3, a3)

This is pretty straightforward. Each Vector contains a single ValueSet
(no matter if Indidual/Encoded/AutoIncremented) with a startOffset of 0
and an endOffset of 99.

Now what happens if we have holes in the data=3F So let's assume we don't
have an absorbtion reading for w3 and w4. In our example we only have a
single dependant vector (absorbtion). So we would just leave out the
wavelength values w3 and w4 and we'd be set:

Wavelength  [ w1 w2 w5 w6 ...... w100 ]
Absorbtion  [ a1 a2 a5 w6 ...... a100 ]

In this case, VectorSet.length would only be 98.

But let's assume we have multiple dependant vectors. I can't think of a
good second dependant vector for UV/VIS, so let's call it Vector3. In
this case we can't leave out w3 and w4 because we might have a reading
vor Vector3 there. We could declare that like this:

Wavelength  [ w1 w2 w3 w4 w5 w6 ...... w100 ]
Absorbtion  [ a1 a2 ]   [ a5 w6 ...... a100 ]  <-- two valuesets here
Vector3     [ v1 v2 v3 v4 v5 v6 ...... v100 ]

Again, we have 100 data points. We don't have a value for absorbtion at
a3 and a4, but that is perfectly legal and valid. Absorbtion would use
two valuesets:

   - startOffset 0 - endOffset 1  and
   - startOffset 4 - endOffset 99

All this can be stored without having a Vector.length attribute. In
=66act, what good would it do to explicitly store that Vector3 only has 98
values=3F If we actually need that number, we can easily calculate it
using the function ( sum(endOffsets) - sum(startOffsets) ). Adding the
Vector.length attribute would not increase the expressive power and
would add another point where a file could become inconsistent, making
validation more difficult.

This same argument exmplains why a length attribute in the *ValueSet
elements would not be beneficial. Here, the number of values is even
easier to calculate (endOffset-startOffset).

Consequently, I would suggest to keep the VectorSet.length attribute
defined as the number of data points.

I look forward to seeing you all again ("virtually") tomorrow. :-)

Best wishes,
Burkhard




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