# Plot 3d.m

From Spinach Documentation Wiki

Volume isosurface plotting utility with non-linear adaptive isosurface spacing.The function is useful for NMR data where small cross-peaks must be adequately contoured next to large diagonal peaks. Syntax:

plot_3d(spin_system,spectrum,parameters,ncont,delta,k,signs)

The following functions are used to compute contour levels:

cont_levs_pos=delta(2)*xmax*linspace(0,1,ncont).^k+xmax*delta(1); cont_levs_neg=delta(2)*xmin*linspace(0,1,ncont).^k+xmin*delta(1);

where:

* xmax and xmin are calculated from the spectrum;

* delta is the minimum and maximum elevation (as a fraction of total intensity) of the contours above the baseline. A reasonable value for most 3D spectra is [0.02 0.2];

* ncont is the number of contours, a reasonable value is 20.

* k controls the curvature of the contour spacing function: k=1 corresponds to linear spacing and k>1 bends the spacing curve to increase the sampling density near the baseline. A reasonable value is 2;

* signs can be set to 'positive', 'negative' or 'both' - this will cause the corresponding contours to be plotted.

The following subfields are required inthe parameters structure:

parameters.sweep three widths, Hz

parameters.spins cell array with three character strings specifying the working spins.

parameters.offset three transmitter offsets, Hz

parameters.axis_units axis units ('ppm','Hz','Gauss')