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Extracting data segments from a file

To create a new file that contains only some of the channels in the original file, there are two possible approaches, 1) remove the unwanted channels, and 2) transfer only the desired channels.  To remove a channel, select it by clicking somewhere in the channel itself or by clicking its associated channel number button (the channel does not have to be visible to be selected this way).  Then choose “Edit > Remove Waveform”.  To copy a channel, use control-c (command-c on a Mac).  This is a keyboard shortcut for “Edit > Copy”.  Only the selected area of the selected channel is copied, so choose “Edit > Select All” (control/command-a in recent versions of AcqKnowledge) before copying.  If the destination graph window already exists and contains data, select the window and choose “Edit > Insert Waveform”.  If the window does not yet exist, choose “File > New…” (control/command-n), and “OK” the default choice of “Graph Window”.  Then choose “Edit > Paste” (control/command-v).  This will only work for the first channel in a file; otherwise the “Paste” option adds the data at the current cursor position of the selected waveform.
 
Although the number of steps required to copy a waveform from one window to another is more than the number required to remove a waveform, if the number of waveforms to be placed in the destination file is smaller than the number of waveforms that are not to be copied, the second approach may be more efficient overall.
To transfer only some of the data from each channel, the most efficient method in recent AcqKnowledge versions is to use the I-beam tool or selection palette (“Display > Show > Selection Palette” or control/commnd-shift-=) to select an area of the graph.  Then choose “File > Save Selection As…”.  This will produce a new file containing all of the channels, but only the selected area of each. 
 
For older AcqKnowledge versions that do not have the “Save Selection As” option, there are again two possible approaches, 1) remove the sections before and after the section to be saved, and 2) copy the selected area from each channel.  To carry out the first option, use “Edit > Clear All” to remove the selected area of all channels at once.  To carry out the second option, follow the steps laid out in the first paragraph of this Knowledge Base entry except for the “Edit > Select All” step.  Instead, select the area to be retained.  Then switch from the I-beam tool to the arrow cursor tool so that the selected area isn't changed if other channels are selected by clicking on them within the graph area.
 
Page last modified 24Dec2014

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