Frida uses its own file format for saving and loading data and curve files. It can also read several legacy formats.

Current format: .yda

The native Frida format uses the extension .yda. It is a plain-text YAML file with the following top-level keys:

• Meta — format identifier and file type
  • format: "yaml/frida 2.0"
  • type: "generic tabular data" or "frida2 curve"
• History — sequence of strings documenting all operations applied to the file (one entry per operation)
• Coord — coordinate metadata
  • x, y: name and unit of the x and y axes
  • z: list of z-coordinate descriptors (name and unit per entry)
• RPar — list of file constants (r0, r1, …), each with name, unit, value, and standard deviation
• Curve (curve files only) — fit model metadata: expression, number of parameters, weighing scheme, and chi-squared
• Slices — the data itself, one entry per spectrum:
  • j: spectrum index
  • z: list of z-values for this spectrum
  • x, y, dy (data files): arrays of x, y, and optional error values
  • p, attr, fitOutcome, fitChi2, … (curve files): parameter values, free/fixed flags, and fit quality metrics

Files are written by the fs command and read by fl.

Export formats

Frida can export data to two plain-text tabular formats:

• .csv — comma-separated values
• .tab — tab-separated values

These formats do not preserve metadata (coordinates, history, etc.). Use them for exchanging data with other programs.

Legacy formats

Frida reads the following older formats:

Extension	Description
.y08	Previous Frida2 binary format (pre-2008)
.a01	Frida1 (Ida) data format
.i96	Frida1 (Ida) data format, 1996 version
.nxs	NeXus/HDF5 format (experimental)

Legacy files are read-only; use fs to re-save them in the current .yda format.