dx-doc 1:4.4.4-7 / usr / share / doc / dx / help / dxall111

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#!CSeaGreen #!N  #!Rall110 Describing the Data #!N #!EC 
#!N #!N To import data through the General Array Importer, you 
must be able to answer the following questions. #!N #!N #!I0 
#!N  #!F-adobe-times-medium-r-normal--18*   #!N #!N #!I30 #!N 1. What are the independent 
and dependent variables? For example, if temperature and wind velocity are 
measured on a latitude-longitude grid, then latitude and longitude are the 
independent variables, temperature and wind velocity the dependent variables. In the 
case of resistance measurements versus the voltage applied to a semiconductor, 
voltage is the independent variable and resistance the dependent variable. #!CIndianRed 
#!N #!N #!N  #!F-adobe-times-bold-r-normal--18*   Components and Variables #!N #!N In Data 
Explorer terminology, the values of the independent variable constitute the "positions" 
component of a data field. In the examples above, the first 
independent variable consists of locations in space and the second does 
not, but both would be represented as "positions" in a data 
field. The independent variable is  #!F-adobe-times-medium-i-normal--18*   always #!EF represented by the 
"positions" component. #!N #!N The values of the dependent variable constitute 
the "data" component. #!N #!N #!EC #!N #!I30 #!N 2. What 
is the dimensionality of the positions and data components? In the 
first example above, latitude and longitude are represented by 2-dimensional positions, 
the temperature by scalar data, and the wind velocity by 2- 
or 3-dimensional vectors. In the second example, voltage is represented by 
1-dimensional positions and the resistance by scalar data. #!N #!I30 #!N 
3. How is the independent variable (the set of positions) to 
be described? By a regular grid (which can be completely described 
by an origin and a set of deltas) or by an 
explicit list (which may or may not be part of the 
data file)? For example, data measurements might be on a grid 
of 1-degree increments in latitude and 5-degree increments in longitude; voltage 
levels might be a set of unrelated values stored with the 
resistances in the data file. #!N #!I30 #!N 4. How are 
the positions connected to one another, if they are connected? For 
example, a regular grid of positions might be connected by a 
regular grid of connections (lines, quads, or cubes). The connections specify 
how data values should be interpolated between positions. Positions that are 
explicitly specified (i.e., not regular) can also be connected by a 
regular grid of connections (e.g., if the grid is deformed, or 
warped). See  #!Lgrdtyps11,dxall111 f Figure 11  #!EL  . #!Cbrown #!N  #!F-adobe-times-medium-r-normal--18*    #!Rgrdtyps11 #!N Graphics omitted 
from Online Documentation. Please see the manual. #!N #!N Figure 11. 
Examples of Grid Types. The three grids in the top row 
represent surfaces; those in the bottom row, volumes. Reading from left 
to right, the three types of grid are: irregular (irregular positions, 
irregular connections), deformed regular (irregular positions, regular connections), and regular (regular 
positions, regular connections), #!EF #!N #!EC #!Cbrown #!N  #!F-adobe-times-medium-r-normal--18*    #!Rcoldpnd12 #!N 
Graphics omitted from Online Documentation. Please see the manual. #!N #!N 
Figure 12. Examples of Data Dependency. In the visualization on the 
left, data correspond one-to-one with positions. Other data values (and colors) 
are interpolated linearly between positions. In the visualization on the right, 
the elements connecting positions are quads. Data (and colors) correspond one-to-one 
with, and are constant within, each quad. #!EF #!N #!EC Note: 
The General Array Importer supports only regular connections (lines, quads, and 
cubes) or scattered data. For irregular connections such as triangles or 
tetrahedra, you can use the Data Explorer native format to import 
your data. (See IBM Visualization Data Explorer User's Guide.) #!N #!I30 
#!N 5. What is the format of the stored data values, 
ASCII or binary? Are they floating point, integer, signed or unsigned 
byte, etc.? #!N #!I30 #!N 6. Are the data dependent on 
"positions" or on "connections"? That is, are the data values associated 
one-to-one with positions or with the connections between positions? See  #!Lcoldpnd12,dxall111 f Figure 12  #!EL  
. (Data associated with connections are often referred to as "cell-centered.") 
With position-dependent data, values between positions are interpolated within the connection 
element. With connection-dependent data, values are assumed to be constant within 
the connection element. #!N #!I30 #!N 7. Do these data values 
represent "series data" or do they constitute only a single frame 
of data? In the example of resistance levels versus voltage, data 
may exist for each of a number of different doping levels. 
Each doping level could be considered a single data field and 
the collection treated as a series. #!N #!I30 #!N 8. Is 
the data in "record" or "spreadsheet" style? (See  #!Lboxes114,dxall113 f Figure 14  #!EL  .) #!N 
#!I30 #!N 9. If the data are on a grid, what 
is the order of the data items with respect to the 
grid? Is it column majority (first index varies fastest) or row 
majority (last index varies fastest)? (See  #!Lrowcol13,dxall111 f Figure 13  #!EL  .) #!N #!I30 #!N 
10. What kind of embedded text (comments, etc.) in the data 
file must be "skipped" when the data values are read? #!N 
#!I0 #!N #!EF #!N #!N #!N With the answers to these 
questions, you can now use the General Array Importer to describe 
your data. #!Cbrown #!N  #!F-adobe-times-medium-r-normal--18*    #!Rrowcol13 #!N Graphics omitted from Online 
Documentation. Please see the manual. #!N #!N Figure 13. Row- versus 
Column-Majority Grids. The two grids shown here are generated from the 
same data file, consisting simply of the numbers 1, 2, 3, 
..., 20. The associated header files differ only in the specification 
of the grids' majority. #!EF #!N #!EC #!N #!N #!N  #!F-adobe-times-medium-i-normal--18*   
Next Topic #!EF #!N #!N  #!Lall111,dxall112 h Creating a Header File  #!EL  #!N  #!F-adobe-times-medium-i-normal--18*   #!N