Section

Column

width	250px

Column

width	60%

Panel

Objectives

Set-up a cylindrical projection over the United States.
Apply land-sahding shading on the coastlines.
Load a grib GRIB file containing Mean-Sea level Presssure and visualise it using black isolines.
Load a grib GRIB file containing Precipitation and visualise it using shading technique.
Add a legend.Add a text.
Draw the position of New-York City
Draw a line to materialise the Xsection we are going to visualise in a next tutorial
Add a text.

You will need to download

Setting of the geographical area

The Geographical geographical area we want to work with today is defined by its lower-left corner [20^oN, 110^oEW] and its upper-right corner [70^oN, 30^oEW].

Have a look at the subpage documentation to learn how to setup a projection .

Section

Column

width	50%

Info

title	Parameters to check

Useful subpage parameters
subpage_lower_left_longitude
subpage_lower_left_latitude
subpage_upper_right_longitude
subpage_upper_right_latitude

Code Block

theme	Confluence
language	python
title	Python - Setting a projection
collapse	true

from Magics.macro import *
#setting the output 
output = output(    
                output_formats = ['png'],
                output_name = "map_step1",
                output_name_first_page_number = "off"
        )
    
#settings of the geographical area 
area = mmap(subpage_map_projection="cylindrical",
        subpage_lower_left_longitude=-110.,
        subpage_lower_left_latitude=20.,
        subpage_upper_right_longitude=-30.,
        subpage_upper_right_latitude=70.,
    )    
#Using a default coastlines to see the result
plot(output, area, mcoast())

Column

width	200px

Image Added

Image Removed

Section

Column

width	200px

...

Setting the coastlines

Until now you have used the mcoast to add coastlines to your plot. The mcoast object comes with a lot of parameters to allow you to style your coastlines layer.

The full list of parameters can be found in the Coastlines documentation.

In this first exercise, we will like to see:

The land coloured in cream.
The coastlines in grey.
The grid as a grey dash line.

Section

Column

width	50%

Info

title	Parameters to check

Useful Coastlines parameters
map_coastline_land_shade
map_coastline_land_shade_colour
map_coastline_colour
map_grid_colour
map_grid_line_style

Code Block

theme	Confluence
language	python
title	Python - Coastlines
collapse	true

from Magics.macro import *
#setting the

Have a look at the PNG output documentation to see which parameters are available to set-up a PNG output.

To create a PNG output Magics, you have to create an output object and to insert at the first position in the plot command

Code Block

theme	Confluence
language	python
title	Python - Output
collapse	true

Section

from Magics.macro import * #settings of the png

 output 
output = output(

    
                output_formats = ['png'],

output_name = "

magics

map_step2",

output_name_first_page_number = "off"
        )

#The plot commad will create a png output called magics.png plot(output, mcoast())

Setting the coastlines

The object mcoast allows the parametrisation of the coastlines.

Have a look at the Coastlines documentation to see which parameters are available.

To configure the look of your coastlines you have to create a mcoast object with the parameters you want.

The mcoast object has to be inserted in the plot command.

Column

width	50%

Code Block

theme	Confluence
language	python
title	Python - Coastlines
collapse	true

from Magics.macro import *

#settings of the png output 
output = output(
			output_formats = ['png'],
  			output_name = "coast",
    		output_name_first_page_number = "off"
    )
##settings of the coastlines attributes 
coast = mcoast(
  map_coastline_land_shade#settings of the geographical area 
area = mmap(subpage_map_projection="cylindrical",
        subpage_lower_left_longitude=-110.,
        subpage_lower_left_latitude=20.,
        subpage_upper_right_longitude=-30.,
        subpage_upper_right_latitude=70.,
    )     
 #settings of the caostlines
coast = mcoast(map_coastline_land_shade = "on",
      map_coastline_land_shade_colour = "cream",
      map_grid_line_style = "dash",
      map_grid_colour = "grey",
      map_label = "on",
  map_coastline_land_shade_colour = "cream",
  map_gridcoastline_line_stylecolour = "dashgrey")
plot(output,
  map_grid_colour = "brown",
  map_label_colour = "brown",
  map_coastline_colour = "brown"
)

#The plot command will now use the coast object
plot(output, coast)

Column

width	200px

Image Removed

Adding a text

Magics allows the user to add of or several lines of text. The position of the text is by default above the plot, but some parameters aloow it to be moved around.

A basic html formatting can be used for colour, style, and font size.

The mtext object has to be inserted in the plot command to see the text on the result.

area, coast)

Column

width	200px

Image Added

Visualising the Mean Sea Level Pressure field

The visualisation of any data in Magics is done by combining 2 kind of objects. One, the Data Action, is used to define the data and explain to Magics how to interpret it, the other one is called Visual Action and will define the type of visualisation and its attributes.

In this example our data are in a GRIB file msl.grib. The Data Action to be used is mgrib in is documented in Grib Input Documentation.

The visualisation we want to apply is a basic contouring mcont, using black for the lines. We want an interval of 5 hPa between isolines. We also want to add an automatic legend, with our own text "Mean Sea Level Pressure". Follow the link to access the Contouring Documentation.

Section

Column

width	50%

Info

title	Parameters to check

mgrib action to load the data
grib_input_file_name

mcont action to define a contouring
contour_line_colour
contour_line_thickness
contour_highlight_colour
contour_highlight_thickness
contour_hilo
contour_level_selection_type
contour_interval
legend
contour_legend_text

Code Block

theme	Confluence
language	python
title	Python - Msl Visualisation
collapse	true

from Magics.macro import *
#setting the output 
output = output(    
                output_formats = ['png'],
                output_name = "map_step3",
                output_name_first_page_number = "off"
        )
#settings of the geographical area 
area = mmap(subpage_map_projection="cylindrical",
        subpage_lower_left_longitude=-110.,
        subpage_lower_left_latitude=20.,
        subpage_upper_right_longitude=-30.,
        subpage_upper_right_latitude=70.,
    )     
 #settings of the caostlines
coast = mcoast(map_coastline_land_shade = "on",
      map_coastline_land_shade_colour = "cream",
      map_grid_line_style = "dash",
      map_grid_colour = "grey",
      map_label = "on",
      map_coastline_colour = "grey")
#Loading the msl Grib data
msl = mgrib(grib_input_file_name="msl.grib")
#Defining the controur
contour = mcont(contour_highlight_colour= "black",
                contour_highlight_thickness= 4,
                contour_hilo= "off",
                contour_interval= 5.,
                contour_label= "on",
                contour_label_frequency= 2,
                contour_label_height= 0.4,
                contour_level_selection_type= "interval",
                contour_line_colour= "black",
                contour_line_thickness= 2, 
                legend='on',
                contour_legend_text= "Mean Sea Level Pressure",
            )
plot(output, area, coast, msl, contour)

Column

width	200px

Image Added

Visualising the precipitation field

The goal of this exercise is to discover a bit more the diverse styles of visualisation offered by the mcont object.

We are pre-processed a GRIB field containing the precipitation accumulated in the last 6 hours of the valid time. We want to disable the automatic scaling appled by Magics and use our own scaling factor, in this case 1000.

Here we will work with shading, and we will use a different technique to setup the levels we want to contour.

We want to use the following list of levels for contouring [0.5, 2., 4., 10., 25., 50., 100., 250.]

and the following list of colours ["cyan", "greenish_blue", "blue", "bluish_purple", "magenta", "orange", "red", "charcoal"]

Section

Column

width	50%

Info

title	Parameters to check

mgrib action to load the data
grib_input_file_name
grib_automatic_scaling
grib_scaling_factor

mcont action to define a contouring
contour_level_selection_type
contour_level_list
contour_shade
contour_shade_method
contour_shade_colour_method
contour_level_selection_type
contour_shade_colour_list
legend

Code Block

theme	Confluence
language	python
title	Python - Use of Shading
collapse	true

#setting the output 
output = output(    
                output_formats = ['png'],
                output_name = "map_step4",
                output_name_first_page_number = "off"
        )
#settings of the geographical area 
area = mmap(subpage_map_projection="cylindrical",
        subpage_lower_left_longitude=-110.,
        subpage_lower_left_latitude=20.,
        subpage_upper_right_longitude=-30.,
        subpage_upper_right_latitude=70.,
    )     
 #settings of the caostlines
coast = mcoast(map_coastline_land_shade = "on",
      map_coastline_land_shade_colour = "cream",
      map_grid_line_style = "dash",
      map_grid_colour = "grey",
      map_label = "on",
      map_coastline_colour = "grey")
#definition of the input data
precip = mgrib(grib_input_file_name="precip.grib", 
    grib_automatic_scaling='off', 
    grib_scaling_factor=1000.)
shading = mcont( contour_highlight= "off",
    contour_hilo= "off",
    contour_label="off",
    contour_level_list=[0.5, 2., 4., 10., 25., 50., 100., 250.],
    contour_level_selection_type= "level_list",
    contour_shade= "on",
    contour_shade_method= "area_fill",
    contour_shade_colour_method= "list",
    contour_shade_colour_list= ["cyan", "greenish_blue", "blue", "bluish_purple", "magenta", "orange", "red", "charcoal"],
    legend="on")
    
plot(output, area, coast, precip, shading)

Column

width	200px

Image Added

Overlaying the 2 layers and playing with legend

Here, we want to demonstrate the plot command.

The actions added to the plot command will be executed sequentially, and their result will be displayed from the background to the foreground .

Then, try to put the shaded layer (precipitation) behind the contoured layer (msl)

and try to improve the legend to make it look continuous, by checking the Legend Documentation.

Section

Column

width	50%

Info

title	Parameters to check

Useful legend parameters
legend
legend_display_type
legend_text_colour
legend_text_font_size

Code Block

theme	Confluence
language	python
title	Python - Overlay
collapse	true

from Magics.macro import *
#setting the output 
output = output(    
                output_formats = ['png'],
                output_name = "map_step5",
                output_name_first_page_number = "off"
        )
#settings of the geographical area 
area = mmap(subpage_map_projection="cylindrical",
        subpage_lower_left_longitude=-110.,
        subpage_lower_left_latitude=20.,
        subpage_upper_right_longitude=-30.,
        subpage_upper_right_latitude=70.,
    )     
 #settings of the caostlines
coast = mcoast(map_coastline_land_shade = "on",
      map_coastline_land_shade_colour = "cream",
      map_grid_line_style = "dash",
      map_grid_colour = "grey",
      map_label = "on",
      map_coastline_colour = "grey")
#definition of the input data
precip = mgrib(grib_input_file_name="precip.grib", 
    grib_automatic_scaling='off', 
    grib_scaling_factor=1000.)
#definition of shading
shading = mcont( contour_highlight= "off",
    contour_hilo= "off",
    contour_label="off",
    contour_level_list=[0.5, 2., 4., 10., 25., 50., 100., 250.],
    contour_level_selection_type= "level_list",
    contour_shade= "on",
    contour_shade_method= "area_fill",
    contour_shade_colour_method= "list",
    contour_shade_colour_list= ["cyan", "greenish_blue", "blue", "bluish_purple", "magenta", "orange", "red", "charcoal"],
    legend="on")
#definition of msl
msl = mgrib(grib_input_file_name="msl.grib")
#Definition of the black contouring
contour = mcont( contour_highlight_colour= "black",
                contour_highlight_thickness= 4,
                contour_hilo= "off",
                contour_interval= 5.,
                contour_label= "on",
                contour_label_frequency= 2,
                contour_label_height= 0.4,
                contour_legend_text= "Mean Sea Level Pressure",
                contour_level_selection_type= "interval",
                contour_line_colour= "black",
                contour_line_thickness= 2,
                legend='on'
            )
#Definition of the legend
legend = mlegend(legend='on', 
            legend_display_type='continuous', 
            legend_text_colour='charcoal', 
            legend_text_font_size=0.4,
            )    
plot(output, area, coast, precip, shading, msl, contour, legend)

Column

width	200px

Image Added

Adding the position of New York City

To demonstrate the use of symbols plotting, we are going to add a big red dot where New York City is.We will the add the text NYC in black on top of the dot.

The position of New York is [41^oN, 74^oW], we can give this position to Magics using the minput object, documented in Input Data Page.

The symbol is performed using the msymb object. You can find the full options in the Symbol Documentation.

Section

Column

width	50%

Info

title	Parameters to check

Useful input parameters
input_x_values
input_y_values

Useful Symbol parameters
symbol_colour
symbol_marker_index
symbol_height
symbol_type
symbol_text_list
symbol_text_font_size
symbol_text_font_colour
symbol_text_font_style
symbol_text_position

Code Block

theme	Confluence
language	python
title	Python - Adding New-York City
collapse	true

from Magics.macro import *
#setting the output 
output = output(    
                output_formats = ['png'],
                output_name = "map_step6",
                output_name_first_page_number = "off"
        )

             
#---------------------------------------
# definition of the previsous layers 
# ...
# ...
#---------------------------------------
#definition of New-York city
new_york = minput(
            input_x_values    =    [-74.],
            input_y_values    =    [41.]
            )
#definition of the symbol
point = msymb(
            symbol_type    =    "both",
            symbol_text_list    =    ["NYC"],
            symbol_marker_index    =    28,
            symbol_colour    =    "red",
            symbol_height    =    0.5,
            symbol_text_font_size = 0.40,
            symbol_text_font_colour = "black",
            symbol_text_position = "top",
            symbol_text_font_style = "bold ", 
            )
plot(output, area, coast, precip, shading, msl, contour, new_york, point, legend)

Column

width	200px

Image Added

Adding a line to show our next Cross-section

In the next exercise, we will display a Cross-section of the Vorticity across the Storm.

We want to show this line of our plot as a black thick line.

The stating point is [50^oN, 90^oW], the end point is [30^oN, 60^oW] : it can be passed to Magics using the minput object, documented in Input Data Page.

To draw the line we will use the mgraph object. All the parameters are available in the Graph Plotting Documentation.

Section

Column

width	50%

Info

title	Parameters to check

Useful input parameters
input_x_values
input_y_values

Useful Graph parameters
graph_line
graph_line_colour

Code Block

theme	Confluence
language	python
title	Python - Adding a line
collapse	true

from Magics.macro import *
#setting the output 
output = output(    
                output_formats = ['png'],
                output_name = "map_step7",
                output_name_first_page_number = "off"
        )

             
#---------------------------------------
# definition of the previous layers 
# ...
# ...
#---------------------------------------
#definition of the Xsection Line
xsection = minput(
            input_x_values    =    [-90., -60.],
            input_y_values    =    [50., 30.]
            )
#definition of the graph
line = mgraph( 
            graph_line_colour    =    "black",
            graph_line_thickness    =    4
            )
plot(output, area, coast, precip, shading, msl, contour, new_york, point, xsection, line, legend)

Column

width	200px

Image Added

Adding a title

We have now a very nice plot... let's add a title at the top.

Text box can be embedded everywhere on a plot, but the default position will be a title at the top of the plot, above an potential legend.

The text facility is documented in the Text Plotting Page.

Section

Column

width	50%

Info

title	Parameters to check

Useful Text parameters
text_lines
text_font_size
text_colour
text_font_style

Code Block

theme	Confluence
language	python
title	Python - Adding a text
collapse	true

from Magics.macro import *
#setting the output 
output = output(    
                output_formats = ['png'],
                output_name = "map_step8",
                output_name_first_page_number = "off"
        )

             
#---------------------------------------
# definition of the previous layers 
# ...
# ...
#---------------------------------------
#definition of the text
title = mtext(text_lines=['Sandy', '30th of October 2012'],
            text_font_size = 0.8,
            text_colour= "charcoal",
            text_font_style='bold',
        )
plot(output, area, coast, precip, shading, msl, contour, new_york, point, xsection, line, legend

Column

width	50%

Code Block

theme	Confluence
language	python
title	Python - Title
collapse	true

from Magics.macro import * #settings of the png output output = output( output_formats = ['png'], output_name = "coast", output_name_first_page_number = "off" ) ##settings of the coastlines attributes coast = mcoast( map_coastline_land_shade = "on", map_coastline_land_shade_colour = "cream", map_grid_line_style = "dash", map_grid_colour = "brown", map_label_colour = "brown", map_coastline_colour = "brown" ) ##settings of the text (notice the Html formatting) title = mtext( text_lines = ["Hello World!", " <b>This is my first plot</b> !"], text_font_size = "0.7", text_colour = "charcoal" ) #The plot command will now use the coast and title objects plot(output, coast

, title)

Column

width	200px

Image Added

Image Removed

Go to the next step...

Go back to the main page ...

Space shortcuts

Page tree

Versions Compared

Old Version 7

New Version Current

Key

Setting of the geographical area

Setting the coastlines

Setting the coastlines

Adding a text

Visualising the Mean Sea Level Pressure field

Visualising the precipitation field

Overlaying the 2 layers and playing with legend

Adding the position of New York City

Adding a line to show our next Cross-section

Adding a title

Space shortcuts

Page tree

Page History

Versions Compared

Old Version 7

New Version Current

Key

Setting of the geographical area

Setting the coastlines

Setting the coastlines

Adding a text

Visualising the Mean Sea Level Pressure field

Visualising the precipitation field

Overlaying the 2 layers and playing with legend

Adding the position of New York City

Adding a line to show our next Cross-section

Adding a title