Skip to content

Latest commit

 

History

History
109 lines (74 loc) · 4.37 KB

track.rst

File metadata and controls

109 lines (74 loc) · 4.37 KB
Raw

Track object

How to use a Track?

The following CSV file is taken from the Storm track <gallery_storm_track> gallery example and has the following structure:

20121027 00 -76.9 27.1
20121027 12 -76.29 28.37
20121028 00 -74.64  30.2
20121028 12 -73.07 31.77
20121029 00 -70.87 33.66
...

So this data contains no header and the separator is a whitespace. Using Track we can make plot in a few lines:

import metview as mv

filename = "sandy_track.grib"
if mv.exist(filename):
    g = mv.read(filename)
else:
    g = mv.gallery.load_dataset(filename)

tr = mv.Track(path, sep=" ")
mv.plot_maps(tr, view=mv.make_geoview(style="grey_2", area="north_america"))

image

Compare this code to the one used in the gallery example to see how much we can simplify the plotting with Track.

Customising the style

The style for Track is taken from the current style configuration. The default style is a list of an mgraph (defining the curve) and an msymb (defining the labels), in that order. The main difficulty is that the labels must be added as a list of str to the msymb, therefore the style is not fixed but must always be generated from the current data. Luckily Track does it automatically for you.

Custom styles can also be used when plotting tracks with plot_maps. Due to the difficulties with the label generation the recommended way for doing it is to derive a new style by updating the default one:

import metview as mv

filename = "sandy_track.grib"
if mv.exist(filename):
    g = mv.read(filename)
else:
    g = mv.gallery.load_dataset(filename)

# create track 
tr = mv.Track(path, sep=" ")

# update style
vd = tr.style().update(
    {"graph_line_colour": "blue", 
    "graph_symbol_colour": "purple",
    "graph_symbol_height": 0.6}, verb="mgraph")

vd = vd.update({"symbol_advanced_table_text_font_size": 0.6}, verb="msymb")

# generate plot
mv.plot_maps(tr, vd,
            view=mv.make_geoview(style="grey_2", area="north_america"))

image

Limitations

Track offers a high-level interface and uses pre-defined settings, therefore it comes with certain limitations:

  • the date format must be yyyymmdd
  • the time format must be hh
  • the label format is hard-coded as dd/hh
  • it cannot be plotted with plot

Note

If you would like to create a fully customised track plot from CSV data see the Storm track <gallery_storm_track> gallery example (it uses read_table, input_visualiser, mgraph and msymb to build the track).