Using Data files

CFTool reads and writes simple text-based data files. Each file consists of columns of numerical data separated by tabs or commas (other separators are also recognised).

By default, CFTool saves data in two, three or four (if x errors are enabled) columns:

Column	Meaning
x-data	Independent variable
y-data	Dependent variable
σy (sigma y)	Uncertainty in y (optional)
σx (sigma x)	Uncertainty in x (optional)

These files can be opened, edited, and re-saved directly within CFTool, or viewed in any spreadsheet or text editor.

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Opening data files

Use File → Load Data to import a text file.

When you open a file:

• The data are plotted immediately in the main figure window with temporary labels.
• If the file contains header rows (lines of text at the top), a dialog appears asking whether to use the top line as axis labels.
• If the file contains more than two numerical columns, a dialog prompts you to choose which columns represent x, y, and σy.

Tip: CFTool automatically recognises tab- or comma-separated formats from most spreadsheets.

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File structure and saving

• Two-column files are assumed to be ordered as x then y.
  (You can later swap axes using Edit → Swap x and y if needed.)
  In this case, CFTool will save immediately without additional prompts.
• Multi-column files require you to select which columns correspond to x, y, and σ the first time you open them.
  On the first save, CFTool will warn before overwriting; subsequent saves proceed normally.

When you choose Save Data, the file is written in the format: x y σ (columns separated by tabs).

Note: If you wish to preserve the original data file, always Save As under a new name before editing.

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Summary

Action	Result
Open file	Data plotted in main window
File has text headers	Prompt to use top line as axis labels
File has >2 columns	Prompt to assign x, y, σ
Two-column file	Assumed x then y
Save	Overwrites original unless saved under a new name
Save As	Writes tab-separated x, y, σ columns