TIME SCALE ADJUSTMENT... This is a specialized operation that has to be used with care. It is primarily intended to equalize the effective sampling rates of two files that you want to merge or append. This is done in one of two ways, depending on the old and new sampling rates. It is important to note that even if you add points, you do NOT add information. And if you make the file smaller, information will be LOST. Therefore, it is a good idea to make a copy of the file before you perform this manipulation.
• If the new rate is “faster” than the old rate (i.e., more samples per unit time), LabAnalyst will add the extra data points by interpolation. For a simple example, if the original sample rate was one Hz (one sample per second) and you want to change that to two Hz (two samples per second), the program will fit one additional data point between each of two successive existing points. The new point will have a value that is the mean of the two points surrounding it. The operation is similar, but more complex, if the new and old sample rates are not integral multiples of each other.
As mentioned earlier, don’t make the mistake of thinking that because you have added more data points, you somehow have added information content.
• If the new rate is “slower” than the old rate (i.e., fewer samples per unit time), LabAnalyst will simply remove data points as appropriate. It does not do any averaging. Consequently, this operation reduces the amount of information in the file…. so use with care (and backup copies if you are wise).
These operations are transient unless you save the file (or use the ‘Save as’ option to make a copy with a different name). But if you save a time-adjusted file under its original name, the file is permanently changed. You cannot ‘undo’ time adjustment. The time scale adjustment window looks like this:
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