Types of Variables

Each file represents a set of variables. A variable is a set of numerical or alphanumerical values. To each sample may correspond one or more variables. The following types of variables are available in Isatis.neo:

  • Coordinates: this is the X, Y or Z coordinate of the data points gravity centers. Importing a file, each coordinate value must be defined. Otherwise an error message will occur.

  • Numerical: numerical variables can be float or integer variables and are stored in 32 or 64 bits. Storage format for float variables is a question of variable precision. A 64 bits format guarantee a better precision but it will take more place on the machine. In Isatis.neo, coordinates are stored in 64 bits and other roles of variables are stored in 32 bits (by default, but customizable). For the integer variables, it depends on the variable values. An integer 32 bits allows the storage of values until 231, and until 263 with an integer 64 bits.

    Samples are not always analyzed and a variable may not be defined for some samples. An undefined value is set instead. This undefined value will not be taken into account during calculations. Undefined values are identified by a character string which may be specified when importing data (it could be set to "blank character" or "N/A" for example). By default, when reading a file, any "blank character" will be considered as an undefined value.

  • Categorical: this kind of variable is made to deal with categories (with a maximum of 32767 categories). A category is associated to a specific string of characters (corresponding to an integer value) and to a dedicated color. The different categories of the variables are managed via a Catalog. Categories are exclusive and they can not overlap themselves or a category can not contain two others for example.
  • Text: text variables may be loaded in Isatis.neo. They are mainly used for selections and displays.

  • Selection: a selection variable corresponds to a binary variable which can take the value 0 or 1 (equal 1 when the data point is inside the selection, 0 otherwise). A sample will be selected if the value of the selection variable is set to 1 and masked off if the value is 0. No undefined value is allowed in a selection variable.

    Many operators of Isatis.neo use a selection during input/read data table or output/write data table. In the input phase, this means that some samples will not be used during the calculation. In the output phase, this means that you do not want the operator to be applied to the masked samples.

    Note that many applications can get a "selection" on the input and/or output data table in order to work only on a subset of the data. This subset can be defined as:

    • a selection variable (only the samples set to 1 will be used),
    • one index of a macro selection variable,
    • one or several categories from a categorical variable.

    A dedicated icon on the right of the selection field allows to invert the selection, which means that the samples previously selected / not selected are respectively unselected / selected.

  • Campaign: the campaign is a dedicated categorical variable. It usually correspond to the date/time when the data have been collected. This campaign name is a way to keep a chronological history of the data. It can be defined when importing data.
  • Macro: we find the macro variables in the simulations outputs. A macro variable refers to the different realizations of the simulations. Each realization can be reachable by a numerical index.

  • Compound: a compound variable is a dedicated variable generally made from two or three components. It can be used to:

    • store rotations or gradients which can be used to define local parameters in kriging with local anisotropies. Rotation and gradient vectors can be built from independent variables respectively in Create Rotation or Create Gradient. Or they can be directly computed in Local Anisotropies.
    • define a sub-block grid (i.e. a grid made from cells of irregular size). A sub-block grid is defined by a points data table and a vector variable defining the size DU/DV(/DW) of each cell along each direction U/V(/W) with a potential rotation (global to the grid). In this case the vector variable is built in Create Block Definition from independent variables (previously imported). Variables require to be defined with a Length Unit Class.

Note: Some variables are structural, that is to say they are always associated to a specific data table. For example lines always contain a Line Name variable, this is a mandatory variable. The contents of these variables cannot be modified (except by specialized operators). This is obviously the case for all the calculated variables but also for the coordinate variables. In Isatis.neo, samples must always refer to true coordinates and undefined values are prohibited in variables taken as coordinates. Then, to avoid any problem, coordinate variables cannot be modified by mistake. The only way to modify a coordinate is to use the Variable Editor functionality.