require 'nyaplot'
require 'mapnya'

true

Case3: Plot wind vectors on the map

Next, let's generate plot vectors on the map. I prepared the data of wind vectors on 2011/01/01, from the website of NASA poddac. I converted NetCDF distributed in the database to CSV file with ruby-netcdf.

path = File.expand_path("../data/wind.csv", __FILE__)
df = Nyaplot::DataFrame.from_csv(path)

index	lat	lon	uwnd	vwnd
0	-78.375	0.125	1.733504295349121	-3.9492156505584717
10	-78.375	2.625	2.0234389305114746	-4.730513095855713
20	-78.375	5.125	2.0112311840057373	-5.069279193878174
30	-78.375	7.625	1.748763918876648	-5.585057735443115
40	-78.375	10.125	1.1780503988265991	-6.186290740966797
50	-78.375	12.625	1.2970762252807617	-5.874992370605469
60	-78.375	15.125	0.9491546154022217	-5.469083786010742
70	-78.375	17.625	0.47915521264076233	-5.066226959228516
80	-78.375	20.125	0.21973997354507446	-4.443630695343018
90	-78.375	22.625	-0.5310382843017578	-4.147592067718506
100	-78.375	25.125	-0.9644143581390381	-3.9125924110412598
110	-78.375	27.625	-0.6531160473823547	-3.5921382904052734
120	-78.375	30.125	-1.0376609563827515	-3.26252818107605
130	-78.375	32.625	-1.287920355796814	-2.7162301540374756
140	-78.375	35.125	-1.0620765686035156	-2.151620626449585
150	-78.375	37.625	-0.4455838203430176	-1.2024660110473633
...	...	...	...	...
894230	76.625	357.625	4.30324125289917	5.511810779571533

# Evil pre-processing of data
df.filter!{|row| !(row[:lon] < 200 && row[:lon] > 175)}
df.each_row{|row| row[:uwnd] = row[:uwnd]/3; row[:vwnd] = row[:vwnd]/3}
""

""

plot = Nyaplot::MapPlot.new
vectors = plot.add_with_df(df, :vectors, :lon, :lat)
vectors.dx(:uwnd)
vectors.dy(:vwnd)
plot.show