How can I import a text file into LabChart that doesn't have a time column, and was recorded at a non-selectable sampling rate?

In general, it is possible to import a text file without a time column just by choosing any Sampling Rate from the list in the Text Import Dialog even if this is not the true sampling rate: 
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This is suitable if you are only interested in analyzing parameters not relating to the time axis (for example Maximums and Minimums). 
In the case of analyzing parameters such as the Interval (for example ECG or HRV analysis), then it is critical that the file be imported at the correct sampling rate. 

This can be done with non-standard sampling rates assuming you know the Sampling Rate, and have access to Microsoft Excel, or some other statistics package that can read a text file:

1. Open the text file into Microsoft Excel
2. Create a new Column A (your data should now be in Column B, C, D etc)
3. Set the first cell (A1) to 0
4. Enter this formula into cell A2:
=(A1+(1/sampling rate))

Where sampling rate is the sample speed / rate of your recorded data in seconds. In this example the original sampling rate of the data file was 512 samples per second.

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5. Copy and paste the formula into all remaining cells into Column A.
This will create a time column that will generate the correct sampling rate when imported into LabChart if you import using 'Time in First Column'. 

This can be checked by looking at the last cell in the Excel file - the time value here should correspond to the length of the original recording.