ncvue - A GUI to view netCDF files¶
A minimal GUI for a quick view of netCDF files. Aiming to be a drop-in replacement for ncview.
About ncvue¶
ncvue
is a minimal GUI for a quick view of netCDF files. It is aiming to be
a drop-in replacement for ncview, being slightly more general than ncview,
which targets maps. If ncvue
is used with maps, it supports mostly
structured grids, more precisely the grids supported by cartopy.
ncvue
is a Python script that can be called from within Python or as a
command line tool. It is not supposed to produce publication-ready plots but
rather provide a quick overview of the netCDF file.
The complete documentation for ncvue
is available from:
Quick usage guide¶
ncvue
can be run from the command line:
ncvue netcdf_file.nc
or from within Python:
from ncvue import ncvue
ncvue('netcdf_file.nc')
where the netCDF file is optional. It can also be left out and a netCDF file can
be opened with the “Open File” button from within ncvue
.
Note, ncvue
uses the TkAgg backend of matplotlib. It must be called
before any other call to matplotlib. This also means that you cannot launch it
from within iPython if it was launched with –pylab. It can be called from
within a standard iPython, though.
One can also install standalone applications: the macOS app or the Windows
executable that come with everything needed to run ncvue
including Python.
General layout¶
On opening, ncvue
presents three panels for different plotting types:
Scatter or Line plots, Contour plots, and Maps. This is the look in macOS light
mode (click on figures to open larger pictures):

All three panes are organised in this fashion: the plotting canvas, the Matplotlib navigation toolbar and the pane, where one can choose the plotting variables and dimensions, as well as plotting options. You can always choose another panel on top, and open another, identical window for the same netCDF file with the button “New Window” on the top right.
Map panel¶
If ncvue
detects latitude and longitude variables with a size greater than
1, it opens the Map panel by default. This is the Map panel in macOS dark mode,
describing all buttons, sliders, entry boxes, spinboxes, and menus:

If it happens that the detection of latitudes and longitudes did not work automatically, you can choose the correct variables manually. Or you might use the empty entries on top of the dropdown menus of the latitudes and longitudes, which uses the index and one can hence display the matrix within the netCDF file. You might want to switch of the coastlines in this case.
You might want to switch off the automatically detected “global” option sometimes if your data is on a rotated grid or excludes some regions such as below minus -60 °S.
All dimensions can be set from 0 to the size of the dimension-1, to “all”, or to any of the arithmetic operators “mean”, “std” (standard deviation), “min”, “max”, “ptp” (point-to-point amplitude, i.e. max-min), “sum”, “median”, “var” (variance).
Be aware that the underlying cartopy/matplotlib may (or may not) need a long time to plot the data (with the pseudocolor ‘mesh’ option) if you change the central longitude of the projection from the central longitude of your data, which is automatically detected if “central lon” is set to None. Setting “central lon” to the central longitude of the input data normally eliminates the problem.
Scatter/Line panel¶
If ncvue
does not detect latitude and longitude variables with a size
greater than 1, it opens the Scatter/Line panel by default. This is the
Scatter/Line panel in macOS dark mode, describing all buttons, sliders, entry
boxes, spinboxes, and menus:

The default plot is a line plot with solid lines (line style ‘ls’ is ‘-‘). One can set line style ‘ls’ to None and set a marker symbol, e.g. ‘o’ for circles, to get a scatter plot. A large variety of line styles, marker symbols and color notations are supported.
ncvue
builds automatically a datetime variable from the time axis. This is
correctly interpreted by the underlying Matplotlib also when zooming into or
panning the axes. But it is also much slower than using the index. Selecting the
empty entry on top of the dropdown menu for x uses the index for the x-axis
and is very fast. Plotting a line plot with 52608 time points takes about 2.2 s
on my Macbook Pro using the datetime variable and about 0.3 s using the index
(i.e. empty x-variable). This is especially true if one plots multiple lines
with ‘all’ entries from a specific dimension. Plotting all 10 depths of soil
water content for the 52608 time points, as in the example below, takes also
about 0.3 s if using the index as x-variable but more than 11.1 s when using the
datetime variable.

Contour panel¶
The last panel provide by ncvue
draws contour plots. This is the
Contour panel in macOS dark mode, describing all buttons, sliders, entry
boxes, spinboxes, and menus:

This produces also either pseudocolor plots (‘mesh’ ticked) or filled contour plots (‘mesh’ unticked) just as the Map panel but without any map projection.