2.3.4.2. - Data Arrays
The second kind of array is the data array. While associative arrays are indexed by arbitrary strings or numbers and can store either strings or numbers, data arrays are indexed by consecutive integers (starting from zero, as is the C convention) and hold a specific data type, such as short integer, float, double, etc.
Data arrays must be specifically declared and dimensioned using the
array keyword (unlike associative arrays, which can come into existence when used in
an expression).
The arrays can have one or two dimensions.
The
mca_get() and
image_get() functions can directly fill arrays with data from one- or
two-dimensional detectors.
Data arrays can be used in expressions containing the standard arithmetic operators to perform simultaneous operations on each element of the array. In addition, a subarray syntax provides a method for performing assignments, operations and functions on only portions of the array.
The functions
array_read(), array_dump(), array_copy(), array_op(), array_plot(), array_fit() and
array_pipe() handle special array operations.
The functions
fmt_read() and
fmt_write() transfer array data
to and from binary-format data files.
The functions
mca_get(), mca_put(), image_get() and
image_put() accept array arguments.
The
print command will print data arrays in a concise format on the screen,
giving a count of repeated columns and rows, rather than printing each array
element.
Array data can be placed in shared memory, making the data accessible to other processes, such as image-display or data-crunching programs. The shared arrays can both be read and written by the other processes. The implementation includes a number of special aids for making the processes work smoothly with spec.
The data values of data-array elements are not saved in the user's state file, unlike associative array elements.
- 2.3.4.2.1. - Data Array Usage
2.3.4.2.2. - String Data Arrays
2.3.4.2.3. - Row-wise and Column-wise Sense
2.3.4.2.4. - Shared Memory Arrays