#!F-adobe-helvetica-medium-r-normal--18* #!N #!CSeaGreen #!N #!Rinvdat Invalid Data #!N #!EC #!N #!N Sometimes in the process of collecting or analyzing data, certain regions or positions have no data value associated with them. For example, an instrument may have a "data drop-out" or a simulation may (for whatever reason) produce an invalid entry. Of course, if you are explicitly listing your positions or connections, you can simply leave those positions out when you create your data file. However, if you have a regular grid (for which you simply list the origin of the grid and the delta in each dimension), this is not convenient. Data Explorer has a way to easily handle this situation, using "invalid positions" and "invalid connections" components. These components are discussed in #!Ldatmod,dxall197 h Understanding the Data Model #!EL , but briefly, when present in a Field, they instruct any module processing that Field to completely ignore any position or connection identified in that component. For example, an "invalid positions" component may list the integers 0, 15, and 23. This instructs Data Explorer to ignore the positions 0, 15, and 23 (and the data associated with those positions). #!N #!N You can create these components in a Data Explorer format file (see #!Limd,dxall618 h Importing Data: File Formats #!EL ) or, often more easily, using the Include module. For example, suppose in your data file drop-outs are indicated with a data value of 9999, while all valid data lies in the range 0-100. Then set the #!F-adobe-times-bold-r-normal--18* max #!EF parameter of Include to 9998. Include will then remove or invalidate all of the positions with the value 9999. Note that it is usually preferable to set the #!F-adobe-times-bold-r-normal--18* cull #!EF flag of Include to 0 so that the data values are invalidated rather than actually removed (see Include in IBM Visualization Data Explorer User's Reference). #!N #!N All Data Explorer modules know to ignore invalid data. For example, Streamlines will stop when they reach an invalid element, and Statistics will ignore data values associated with invalid elements. #!N #!N #!N #!F-adobe-times-medium-i-normal--18* Next Topic #!EF #!N #!N #!Lfields,dxall195 h Fields #!EL #!N #!F-adobe-times-medium-i-normal--18* #!N
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