Plotting Many Spectra Together with the Overlay Manager
When a series of spectra is acquired as a single experiment, the spectrometer stores it as a matrix and
the same display options available for 2-D spectra become automatically available.
When the spectra are instead stored as separate 1-D files, they can easily be combined with the Overlay Manager.
The Overlay Manager can also be used to display multiple 2-D spectra simultaneously, each with its own color if desired.
How to Create a Stacked Plot with the Overlay Manager:
- Open and process all the spectra.
- Bring to the front the first spectrum of the series.
- Choose Format > Overlay. The list of open windows appears (the frontmost window is excluded).
- Select the spectra you want to display as overlays by checking the boxes next to their names. To select all the windows at once, click “All”.
- Set the value (in screen points) for the progressive vertical offset between adjacent spectra. With the initial value of zero the spectra are simply superimposed.
- Click Apply to see the effect. You can try with different values. It is easier to adjust this offset when the Overlay Manager is closed: click the bottom overlay and drag it to a new position.
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If the order of the spectra is not correct, try sorting them by clicking the column headers.
If you prefer a custom order, click All to clear the overlay check marks, then enable them again in the desired sequence. The first spectrum you select becomes the bottom of the stack, and each subsequent spectrum is placed above it. The progressive offsets are applied according to this stacking order.
To synchronize the table with the internal stack, choose “List as Stacked” (on the Mac: under the “Order” pull-down menu). - You can set the color for a single overlay: click the corresponding colored rectangle on the left. The “extend” button (on the Mac: an orange arrow) applies the same color scheme to the spectra listed above. An article on the web describes how to create a color gradient.
- If the frequency scale of the overlays is not correct, click Force Same Scale (copies the frequency reference from the frontmost document to the other ones).
- Close the Overlay Manager. The frontmost document stores the links to the overlays. The connection is permanent, unless you rename or delete the files (broken links are immediately forgotten). If you move all the files together, the links remain valid.
In our example, it is not necessary to change the relative amplification of the overlays. If you press the button Fit, the highest peak of the last overlay is scaled to fill the available height. Alternatively, you can enter an explicit value for the amplification. When the dialog is closed, you can use the keys * and / to obtain the same effect.
To adjust amplification or offset values, move the pointer over the corresponding field and rotate the mouse wheel.
When typing the offset values, you are allowed to enter them as percentages (of the window size).
On Windows, you have three fields where the values for the selected overlay are reproduced and can be edited.
If you double-click a name in the table of open windows, the overlay ceases to be a normal overlay and becomes a replica of the corresponding document. The replica retains its own frequency scale, integrals, size, and display settings, and can be positioned independently of the other spectra.
Related Topics
Subtracting a Spectrum from Another
Keyboard Commands to Manipulate the Overlays
Tabulating the Integrals of a Series of Spectra