nccreate_time_1dim.rb - katon @ ウィキ

require "numru/netcdf"
include NumRu

file = NetCDF.create("test3.nc")     # 新規作成
nx = 4
file.def_dim("x",nx)                 # 次元の定義
file.def_dim("t",0)                  # t~UNLIMITED
require "date"
file.put_att("history","created by #{$0}  #{Date.today}")
                                     # グローバル属性の設定
x = file.def_var("lon","sfloat",["x"]) # 変数の定義
t = file.def_var("t","sfloat",["t"])

x.put_att("long_name","longitude") # 属性の設定
x.put_att("units","deg")
t.put_att("long_name","time")
t.put_att("units","s")

velx = file.def_var("VelX","sfloat",["x","t"])
velx.put_att("long_name","longitudinal velocity")
velx.put_att("units","m/s")
file.enddef                          # defineモード終わり

x.put( NArray.float(nx).indgen!*120 )    # 値を入れる

dt = 10.0 # time interval
nt = 3    # total time step  

n=0
for n in 0..(nt-1)
  time = n * dt 
  print "n=#{n}, time=#{time}\n" 
  z = NArray.float(nx).indgen! * n * dt 

  velx.put(z, "start"=>[0,n],"end"=>[-1,n])
                                          # startからendまで値を入れる
  t.put( time, "index"=>[n])              # indexの場所に値を入れる
end

file.close
print `ncdump test3.nc`               # できたファイルを見る

出力結果

$ ruby nccreate_time_1dim.rb 
n=0, time=0.0
n=1, time=10.0
n=2, time=20.0
netcdf test3 {
dimensions:
	x = 4 ;
	t = UNLIMITED ; // (3 currently)
variables:
	float lon(x) ;
		lon:long_name = "longitude" ;
		lon:units = "deg" ;
	float t(t) ;
		t:long_name = "time" ;
		t:units = "s" ;
	float VelX(t, x) ;
		VelX:long_name = "longitudinal velocity" ;
		VelX:units = "m/s" ;

// global attributes:
		:history = "created by nccreate_time_1dim.rb  2012-06-22" ;
data:

 lon = 0, 120, 240, 360 ;

 t = 0, 10, 20 ;

 VelX =
  0, 0, 0, 0,
  0, 10, 20, 30,
  0, 20, 40, 60 ;
}