| 325 | | * (optional) '''!ListGlobalAttribute:''' list (cell array of character strings) of the names of global attributes Att_1, Att_2... |
| 326 | | * (mandatory) '''!ListVarName:''' list of the variable names Var_1, Var_2....(cell array of character strings). |
| 327 | | * (mandatory) '''!VarDimName:''' list of the dimensions associated with each variable: this is a cell array whose number of element is equal to that of '''!ListVarName'''. Each element is the dimension name for a unidimensional variable, or a cell array specifying the list of dimension names for a multidimensional variable. |
| | 325 | * (optional) '''ListGlobalAttribute:''' list (cell array of character strings) of the names of global attributes Att_1, Att_2... |
| | 326 | * (mandatory) '''ListVarName:''' list of the variable names Var_1, Var_2....(cell array of character strings). |
| | 327 | * (mandatory) '''VarDimName:''' list of the dimensions associated with each variable: this is a cell array whose number of element is equal to that of '''!ListVarName'''. Each element is the dimension name for a unidimensional variable, or a cell array specifying the list of dimension names for a multidimensional variable. |
| 344 | | -'''Global attributes active in uvmat''' Those are used for plot settings or data processing. |
| 345 | | -'Conventions': |
| 346 | | |
| 347 | | * ='uvmat/civdata': indicate that the variables are named according to [CIV data description->#civdata]. |
| 348 | | -'CoordMesh': typical mesh for coordinates, used to define default projection grids and mouse selection action. Calculated automatically from the data if not specified. |
| 349 | | -'CoordUnit': character string representing the unit for space coordinates. It is used to distinguish image coordinates (CoordUnit='pixel') and physical (for instance CoordUnit='cm'). If 'CoordUnit' is defined, [projection ->#set_object] will be allowed only on objects with the same 'CoordUnit', and plots will be done by default with axis option 'equal' (same scale for both axis). |
| 350 | | -*Dt: time interval for CIV data. It is used for calibration, to transform displacement into velocity. |
| 351 | | -*Time: real number indicating the time of the field, used to obtain time series from data sets. |
| 352 | | -*TimeUnit: character string representing the unit of time (consistently for Time, Dt and velocity). |
| | 344 | -'''Global attributes active in uvmat''': those are used for plot settings or data processing. |
| | 345 | * 'Conventions': |
| | 346 | * ='uvmat': indicate that the conventions described here are followed |
| | 347 | * ='uvmat/civdata': indicate that the variables are named according to [wiki:#civdata]. |
| | 348 | * '!CoordMesh': typical mesh for coordinates, used to define default projection grids and mouse selection action. Calculated automatically from the data if not specified. |
| | 349 | * '!CoordUnit': character string representing the unit for space coordinates. It is used to distinguish image coordinates (!CoordUnit='pixel') and physical (for instance !CoordUnit='cm'). If '!CoordUnit' is defined, [projection ->#set_object] will be allowed only on objects with the same '!CoordUnit', and plots will be done by default with axis option 'equal' (same scale for both axis). |
| | 350 | * 'Dt': time interval for CIV data. It is used for calibration, to transform displacement into velocity. |
| | 351 | * 'Time': real number indicating the time of the field, used to obtain time series from data sets. |
| | 352 | * '!TimeUnit': character string representing the unit of time (consistently for Time, Dt and velocity). |
| 355 | | -*Project: recalls the project name |
| 356 | | -*Campaign: recalls the campaign name |
| 357 | | -*Experiment: recalls the experiment name(s) of the raw data |
| 358 | | -*DataSeries: recalls the device name (s), if defined, of the raw data |
| 359 | | -*ObjectStyle: ='points', 'line', 'plane', denotes the style of geometric object on which the data have been 'projected'. For instance a profiler project a physical field along a line. |
| 360 | | -*ObjectCoord: Coordinates defining a geometric object on which the data have been projected. |
| 361 | | -*ObjectRangeX, ObjectRangeY, ObjectRangeZ : range of action of a projection object along each coordinate, see section 6. |
| 362 | | -* 'long_name':(convention from [unidata->http://www.unidata.ucar.edu:]) a long descriptive name, could be used for labeling plots, for example. If a variable has no long_name attribute assigned, the variable name should be used as a default. |
| | 355 | * Project: recalls the project name |
| | 356 | * Campaign: recalls the campaign name |
| | 357 | * Experiment: recalls the experiment name(s) of the raw data |
| | 358 | * DataSeries: recalls the device name (s), if defined, of the raw data |
| | 359 | * ObjectStyle: ='points', 'line', 'plane', denotes the style of geometric object on which the data have been 'projected'. For instance a profiler project a physical field along a line. |
| | 360 | * ObjectCoord: Coordinates defining a geometric object on which the data have been projected. |
| | 361 | * ObjectRangeX, ObjectRangeY, ObjectRangeZ : range of action of a projection object along each coordinate, see section 6. |
| | 362 | * 'long_name':(convention from [unidata->http://www.unidata.ucar.edu:]) a long descriptive name, could be used for labeling plots, for example. If a variable has no long_name attribute assigned, the variable name should be used as a default. |
| 365 | | -* Mesh: suggested step value to discretize the values of the variable, used to define the bins for histograms. |
| 366 | | -* Role: it specifies the role of the variable arrays for plotting or processing programs, see below. if Role is not defined variables are considered by default as 'scalar'. |
| 367 | | -* Unit or 'units' (convention from [unidata->http://www.unidata.ucar.edu:]) : char string giving the unit of a variable, used in plot axis labels (overset by global attributes 'CoordUnit' and 'TimeUnit' if defined). |
| 368 | | |
| 369 | | -'''The attribute 'Role':''' The following options are used for the attribute 'role': |
| 370 | | -* 'ancillary': information of secondary use, indicating for instance an error estimate of field variables within a field cell (omitted in plotting) |
| 371 | | -* 'coord_x', 'coord_y', 'coord_z': represents a sets of unstructured coordinates x, y and z for the field variables sharing the same dimension name. |
| 372 | | -* 'coord_tps': coordinates of thin plate shell (tps) centres used for spline interpolation. |
| 373 | | -* 'discrete': field with discrete values (no spatial interpolation), repesented with dots (no line) in 1D plots. |
| 374 | | -* 'errorflag': provides an error flag marking the field variables as false or true within a field cell , default=0, no error. Different non zero values can mark different criteria of elimination, see [section 10.3->#sec10.3] for PIV data. Such flagging is reversible, since the data themselves are not lost. |
| 375 | | -* 'grad_x', 'grad_y', 'grad_z' :represents the x, y or z component of a contravariant vector** (like gradients). |
| 376 | | -* 'image_rgb': represents a color image. The last dimension of the array corresponds to the three color components 'rgb'. -* 'scalar': (default) represents a scalar field |
| 377 | | -* 'tensor': represents a tensor field whose components correspond to the two last dimensions of the array.** |
| 378 | | -* vector: matrix whose last dimension states for the vector components.** |
| 379 | | -* 'vector_x', 'vector_y', 'vector_z' : represents the x, y or z component of a vector (covariant) |
| 380 | | -* 'warnflag': provides a warning flag about the quality of data for the field variables within a field cell., default=0, no warning. |
| | 365 | * Mesh: suggested step value to discretize the values of the variable, used to define the bins for histograms. |
| | 366 | * Role: it specifies the role of the variable arrays for plotting or processing programs, see below. if Role is not defined variables are considered by default as 'scalar'. |
| | 367 | * Unit or 'units' (convention from [unidata->http://www.unidata.ucar.edu:]) : char string giving the unit of a variable, used in plot axis labels (overset by global attributes 'CoordUnit' and 'TimeUnit' if defined). |
| | 368 | |
| | 369 | -'''The attribute 'Role':''' the following options are used for the attribute 'Role': |
| | 370 | * 'ancillary': information of secondary use, indicating for instance an error estimate of field variables within a field cell (omitted in plotting) |
| | 371 | * 'coord_x', 'coord_y', 'coord_z': represents a sets of unstructured coordinates x, y and z for the field variables sharing the same dimension name. |
| | 372 | * 'coord_tps': coordinates of thin plate shell (tps) centres used for spline interpolation. |
| | 373 | * 'discrete': field with discrete values (no spatial interpolation), repesented with dots (no line) in 1D plots. |
| | 374 | * 'errorflag': provides an error flag marking the field variables as false or true within a field cell , default=0, no error. Different non zero values can mark different criteria of elimination, see [section 10.3->#sec10.3] for PIV data. Such flagging is reversible, since the data themselves are not lost. |
| | 375 | * 'grad_x', 'grad_y', 'grad_z' :represents the x, y or z component of a contravariant vector** (like gradients). |
| | 376 | * 'image_rgb': represents a color image. The last dimension of the array corresponds to the three color components 'rgb'. -* 'scalar': (default) represents a scalar field |
| | 377 | * 'tensor': represents a tensor field whose components correspond to the two last dimensions of the array.** |
| | 378 | * vector: matrix whose last dimension states for the vector components.** |
| | 379 | * 'vector_x', 'vector_y', 'vector_z' : represents the x, y or z component of a vector (covariant) |
| | 380 | * 'warnflag': provides a warning flag about the quality of data for the field variables within a field cell., default=0, no warning. |
| 383 | | The variables of field objects are split into {field cells} representing spatial fields. Differerent types of field cells are identified for processing and plotting. This identification is performed by the function {find_field_cells.m} which first groups the variables into cells of variables sharing common variable dimensions, determines their spatial dimension, and idendify the following types. |
| 384 | | |
| 385 | | -*Dimension variables: these are unique unidimensional variable arrays corresponding to a given dimension, leading to a cell with a single variable, dimension 1. This is interpreted as the set of coordinate values associated with this dimension. An alternative possibility, suitable for a coordiante with a constant grid mesh, is a variable array with two values with the same name as a dimension: it then specifies the lower and upper bounds of the coordinate. -* Field cell with unstructured coordinates: this is a cell of variables sharing the same set of unstructured coordinates, indicated by the attribute Role=coord_x, coord_y, coord_z. -* Field cell with structured coordinates: this is a cell of several variable(s) sharing the same set of dimensions associated with variables. (addditional dimension may indicate for instance a vector component, not associated with a coordinate). -* Thin plate shell (tps) field cell: represents a set of coordinates and tps weights in a way suitable for tps interpolation/filter. |
| 386 | | |
| 387 | | The field structure is furthermore indicated by using appropriate names for dimensions, but this is only for documentation, without use in processing functions (except for coordinate dimensions denoting coordinate range, see above). The following conventions are used: -* coord_1,_2,_3: dimension with the same name as a coordinate variable array (coordinate dimension) -* 'nb_coord': denotes the space dimension for vector components -* 'nb_coord_j', 'nb_coord_i': denotes the space dimensions for the two tensor components -* 'rgb' : denotes the diemension of the color component in a true color image. -* 'nb_point' or 'nb_vec' (for vectors) denotes the set of positions with unstructured coordinates. -* 'nb_tps': diemension of the index for the tps centres -* 'nb_subdomain' denotes the dimension for the subdomain index for tps coefficients |
| 388 | | |
| 389 | | [<doc115|right>->#top] |
| | 383 | The variables of field objects are split into {field cells} representing spatial fields. Differerent types of field cells are identified for processing and plotting. This identification is performed by the function ''find_field_cells.m'' which first groups the variables into cells of variables sharing common variable dimensions, determines their spatial dimension, and idendify the following types. |
| | 384 | |
| | 385 | * Dimension variables: these are unique unidimensional variable arrays corresponding to a given dimension, leading to a cell with a single variable, dimension 1. This is interpreted as the set of coordinate values associated with this dimension. An alternative possibility, suitable for a coordiante with a constant grid mesh, is a variable array with two values with the same name as a dimension: it then specifies the lower and upper bounds of the coordinate. |
| | 386 | * Field cell with unstructured coordinates: this is a cell of variables sharing the same set of unstructured coordinates, indicated by the attribute Role=coord_x, coord_y, coord_z. |
| | 387 | * Field cell with structured coordinates: this is a cell of several variable(s) sharing the same set of dimensions associated with variables. (addditional dimension may indicate for instance a vector component, not associated with a coordinate). |
| | 388 | * Thin plate shell (tps) field cell: represents a set of coordinates and tps weights in a way suitable for tps interpolation/filter. |
| | 389 | |
| | 390 | The field structure is furthermore indicated by using appropriate names for dimensions, but this is only for documentation, without use in processing functions (except for coordinate dimensions denoting coordinate range, see above). The following conventions are used: |
| | 391 | * coord_1,_2,_3: dimension with the same name as a coordinate variable array (coordinate dimension) |
| | 392 | * 'nb_coord': denotes the space dimension for vector components |
| | 393 | * 'nb_coord_j', 'nb_coord_i': denotes the space dimensions for the two tensor components |
| | 394 | * 'rgb' : denotes the diemension of the color component in a true color image. |
| | 395 | * 'nb_point' or 'nb_vec' (for vectors) denotes the set of positions with unstructured coordinates. |
| | 396 | * 'nb_tps': dimension of the index for the tps centres |
| | 397 | * 'nb_subdomain' denotes the dimension for the subdomain index for tps coefficients |
| 481 | | In contrast to variables, which are intended for bulk data, attributes are intended for ancillary data, or information about the data. The total amount of ancillary data associated with a NetCDF object, and stored in its attributes, is typically small enough to be memory-resident. However variables are often too large to entirely fit in memory and must be split into sections for processing. |
| 482 | | |
| 483 | | Another difference between attributes and variables is that variables may be multidimensional. Attributes are all either scalars (single-valued) or vectors (a single, fixed dimension). |
| 484 | | |
| 485 | | Variables are created with a name, type, and shape before they are assigned data values, so a variable may exist with no values. The value of an attribute is specified when it is created, unless it is a zero-length attribute. |
| 486 | | |
| 487 | | A variable may have attributes, but an attribute cannot have attributes. Attributes assigned to variables may have the same units as the variable (for example, valid_range) or have no units (for example, scale_factor). If you want to store data that requires units different from those of the associated variable, it is better to use a variable than an attribute. More generally, if data require ancillary data to describe them, are multidimensional, require any of the defined NetCDF dimensions to index their values, or require a significant amount of storage, that data should be represented using variables rather than attributes. |
| | 489 | In contrast to variables, which are intended for bulk data, attributes are intended for ancillary data, or information about the data. The total amount of ancillary data associated with a NetCDF object, and stored in its attributes, is typically small enough to be memory-resident. However variables are often too large to entirely fit in memory and must be split into sections for processing. |
| | 490 | |
| | 491 | Another difference between attributes and variables is that variables may be multidimensional. Attributes are all either scalars (single-valued) or vectors (a single, fixed dimension). |
| | 492 | |
| | 493 | Variables are created with a name, type, and shape before they are assigned data values, so a variable may exist with no values. The value of an attribute is specified when it is created, unless it is a zero-length attribute. |
| | 494 | |
| | 495 | A variable may have attributes, but an attribute cannot have attributes. Attributes assigned to variables may have the same units as the variable (for example, valid_range) or have no units (for example, scale_factor). If you want to store data that requires units different from those of the associated variable, it is better to use a variable than an attribute. More generally, if data require ancillary data to describe them, are multidimensional, require any of the defined NetCDF dimensions to index their values, or require a significant amount of storage, that data should be represented using variables rather than attributes. |
