Data files

File types

FELIX reads and writes datafiles of several different types. Each file type is identified by a three-letter suffix (or extension), preceded by a dot. Some types of user-generated files do not require prefixes (e.g., 3D object files). File names may contain a maximum of 32 characters. The standard default FELIX file types and their extensions are:

Additionally, the .pks and .ppm file formats, used by FELIX and by other Accelrys products, are described in the Common File Formats book.

Although the default file extensions are convenient, they are not mandatory. Commands that access only specific types of files assume the default extension unless a nonstandard extension is specified. For example, the read command (re or rn) is usually used to read unprocessed data files that have .dat default extension. However, FELIX will read datafiles with nonstandard extensions, so long as the file extensions are explicitly stated:

 > re sample.ser
 > re sample.001

The default extensions merely help you to organize your files conveniently, to avoid confusion.

File format for ASCII data files

In addition to the old and new 1D-data file formats, there is also an ASCII datafile format. Historically, there was no way to move data files between computers with different binary data formats. The original FELIX data files (old format) could be read only by the same type of computer that had written them. This is because these data files contained binary representations of the data. The use of ASCII-formatted datafiles was the only way to move data to a different type of computer.

The new format for FELIX datafiles eliminates this problem by using a machine-independent data representation. Now, any computer that uses ANSI standards for its binary data can read and write FELIX 1D datafiles, and the need for ASCII formatted data files has been greatly reduced.

However, for completeness, and for those rare situations where no other method is appropriate, the ASCII data format is still useful. The format is described below.

This data format can contain only a single 1D data spectrum. To hold a complete multidimensional experiment, you need multiple ASCII files, one for each FID.

ASCII data file example

An example, with explicit line numbers, is shown. The line numbers are for reference only; they are not part of the file.

1	 	params 		16
2 2048, 0.20000000E+04
3 1, 0.50000000E+03
4 0, 0.00000000E+00
5 1, 0.00000000E+00
6 0, 0.00000000E+00
7 0, 0.10020406E+02
8 0, -0.23724947E+02
9 0, 0.00000000E+00
10 0, 0.00000000E+00
11 0, 0.00000000E+00
12 0, 0.00000000E+00
13 0, 0.00000000E+00
14 0, 0.00000000E+00
15 0, 0.00000000E+00
16 0, 0.00000000E+00
17 0, 0.00000000E+00
18 data 2048
19 0.29346375E+05 0.81563688E+05 0.29839797E+05 0.82501023E+05
20 0.29120594E+05 0.84976672E+05 0.24982078E+05 0.86691141E+05
21 0.19801203E+05 0.84221766E+05 0.17831391E+05 0.79039844E+05
22 0.18796516E+05 0.75148625E+05 0.19913953E+05 0.72823125E+05
23 0.21470313E+05 0.70696391E+05 0.24038313E+05 0.70447773E+05
24 0.24443797E+05 0.72803344E+05 0.21105609E+05 0.73622492E+05
. . .

ASCII data file format description

Line 1:

This is the parameter header line, which contains the keyword params and the number of parameter data lines. The format is:

     params, i8

Lines 2-17:

These are the data parameters. These lines all contain one integer and one real number. Many of these parameters are unused. The essential parameters are named explicitly. For parameters that are equivalent to a FELIX reserved symbol, the symbol name is given in parentheses. The format is:


Line 2:

This line contains the number of data points (datsiz) and the spectrum width (swidth).

Line 3:

This line contains the data type (datype) and the spectrometer frequency (sfreq).

Line 4:

The first datafield in this line is unused, the second is the reference shift (refsh).

Line 5:

This line contains the axis type (axtype) and the reference point (refpt).

Line 6:

This line is unused.

Line 7:

The first datafield in this line is unused, while the second is the zero-order phase (phase0).

Line 8:

The first datafield in this line is unused, while the second contains the first-order phase (phase1).

Lines 9-17:

These lines are unused.

The reference shift and point symbols are only read in when the axis type is non-zero.
The phases are only read in when they are non-zero.

Line 18:

This is the data header line, which contains the keyword "data" and the number of datapoints. The format is:


Lines 19-24:

The remaining lines contain datapoint values. The format of all these lines is identical. The identity of each value depends on the data type. When the data are complex, the real-number portion precedes the imaginary-number portion for each datapoint. The format is:


Sample data segment for real-number data:

Real_1 Real_2 Real_3 Real_4
Real_5 Real_6 Real_7 Real_8
. . .

Sample data segment for complex-number data:

Real_1 Imag_1 Real_2 Imag_2
Real_3 Imag_3 Real_4 Imag_4
Real_5 Imag_5 Real_6 Imag_6
Real_7 Imag_7 Real_8 Imag_8
. . .

See the FELIX Command Language Reference for more detailed information on reading files.