NMRView facilitates both visual and quantitative analysis of NMR spectra. One of the simplest quantitative measures of the dataset is to calculate some basic statistics. This can be done through the Analysis Panel.
Place the cross hairs so that they form a box around the region you wish to analyze. You can set the cross hair positions by moving them with the mouse, or by entering values in the four entry boxes (x1,y1,x2,y2). Next, click the .
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The results of the analysis are placed in the the labeled fields as follows:
- volume
Return the sum of the points in the region.
- evolume
Return the sum of the points in an ellipse bounded by the region.
- min
Return the minimum value from the region.
- extreme
Return the most extreme (maximum or minimum) value from the cursor region.
- mean
Return the average value in the cursor region.
- center
Return the value at the center of the cursor region.
- jitter
Return the largest value (of the same sign as center point) within a certain tolerance (+/- 25% of the region width) of the center of the cursor region.
- sdev
Return the standard deviation of the values in the curror region.
The values are also stored in a global Tcl variable named
Nv_Value.
It is often useful to look at not only the contour plot of a spectrum with two or more dimensions, but to also look at vector slices through the spectrum. The Extract Panel allows one to extract vectors from the displayed spectrum. The extracted vectors are displayed in a separate "vecGraph" window. The vecGraph window is fundamentally the same as any other spectral display window, but has additional control widgets for interacting with the displayed vector. ither one will extract a 1D spectrum corresponding to the position of your black cursor (in the default color scheme), calling up a new window. Extract/Replace extracts one spectrum for display in a new window , and Extract/Add allows you to overlay multiple 1D spectra in that window.
Figure 6.15. Application of the "Extract/Replace" button in the Spectrum Attributes...Analysis panel
Vectors can either replace any previously existing vector in the vecGraph window, or be displayed along with any existing vectors. This latter mode can be used to easily compare slices at different positions in the spectrum. Note, if multiple spectra are to be extracted into the vecGraph window, then they should have the same axis labels.
- X
Extract the slice parallel to the x-axis defined by crosshair 1.
- Y
Extract the slice parallel to the y-axis defined by crosshair 1.
- Z
Extract the slice parallel to the z-axis defined by crosshair 1.
- A
Extract the slice parallel to the a-axis (z2-axis) defined by crosshair 1.