A real number (or a list of real numbers for multi-channel files) specifying the x-axis value of the first point in each series. Defaults to 0.
A positive real number specifying the sample spacing, i.e. the interval in horizontal units between the data points in a series. The reciprocal of this value, the sampling rate, can be set using the RATE keyword. Only one of the keywords INTERVAL or RATE should be used. Defaults to 1.
A positive real number specifying the sampling rate, i.e. the number of data values present per unit time or space in horizontal units. The reciprocal of this value, the sample interval, can be set using the INTERVAL keyword. Only one of the keywords RATE or INTERVAL should be used. Defaults to 1.