Mathematically speaking, the data stored by netcdf is a single-valued function with multiple independent variables. From the formula, that is, f(x, y, z, ...) = value, and the independent variables x, y and z of the function are called dimension in netcdf?
Or axix, the function value is called variable in netcdf, and some physical properties of independent variables and function values, such as measurement unit (dimension), physical name and so on?
In netcdf, it is called an attribute.
Contents of netcdf file
The structure of netcdf file includes the following objects:?
1, variable?
Variables correspond to real physical data. For example, the electricity meter in our house shows the readings at each moment, indicating the electricity consumption of users at that moment. This reading can be expressed by variables in netcdf. It is a single-valued function with time as independent variable (or the number of independent variables is one dimension). For another example, in meteorology, it is necessary to draw an air pressure map, that is, "What is the air pressure at the point of xx degrees east longitude and yy degrees north latitude?" This is a two-dimensional single-valued function, and the two dimensions are longitude and latitude. The function value is atmospheric pressure.
As can be seen from the above example, the variable in netcdf is an n-dimensional array, the dimension of the array is the number of independent variables in the actual problem, and the value of the array is the observed physical value. There are six storage types of variables (array values) in netcdf: ascii character (char), byte (short), integer (int), float and double. Obviously, these types are consistent with those in C, and friends who engage in C should understand it soon.
2. Dimension?
Dimension corresponds to the independent variable in the function, or the coordinate axis in the function image, which is a component of the n-dimensional vector in linear algebra (this is also the origin of the name dimension). In netcdf, a dimension has a name and a range (or length, that is, a domain in mathematics, which can be a set of discrete points or a continuous interval). In netcdf, the length of a dimension is basically limited, and there can only be an infinite dimension at most.
3. attributes?
The annotation or explanation of attributes to the specific physical meaning of variable values and dimensions. Because variables and dimensions are only in netcdf.