I've got files with cartesian data - a collection of points each coming with 3 coordinates and 3 magnetic field components. I need to visualize this data as 2D plots with magnetic field lines.
How do I do that? What manipulations do I have to do with the original data to be able to plot those vector lines? And what would the gnuplot commands look like?
The command to plot the entire data set as vectors is simple:
set style arrow 1 head filled linewidth 0.5
splot 'data' using 1:2:3:4:5:6 with vectors arrowstyle 1
This assumes that the vector components are given in the same units as your axis coordinates; otherwise you would have to add a scale factor (e.g. replace 4:5:6 with ($4 * scale):($5*scale):($6*scale) However this will generate a 3D plot that may well be too complicated to interpret visually in 2D projection. You might simplify it by specifying a projection along the z axis and then filtering to select only the points in a particular slice of z values:
set view map # projection along z
filter(z) = ((zlow < z && z < zhigh) ? z : NaN)
splot 'data' using 1:2:(filter($3)):4:5:6 with vectors arrowstyle 1
More complicated representations that combine the vectors with contours of an associated magnitude are possible. Have a look at the on-line demo vector dem for an example.
