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I'm using the NetCDF-C++ library (4.3.1), and I want to write a netCDF file
with an unlimited-size dimension. From what I understood from the
documentation, you call the ncFile addDim method without specifying the
size of the data.
When I write my program with that, the netCDF header says that my dimension
is unlimited, but when I look at the variable I used that is directly
associated with that dimension it becomes all nulls... If I specify the
size of that dimension then the data is no longer nulls, but I don't get
the unlimited dimension size. I've got an example below where I want time
to be the unlimited dimension:
NetCDF example
netcdf example {
dimensions:
latitude = 181 ;
longitude = 360 ;
time = UNLIMITED ; // (30 currently)
variables:
float latitude(latitude) ;
latitude:units = "degrees_north" ;
latitude:long_name = "latitude" ;
float longitude(longitude) ;
longitude:units = "degrees_east" ;
longitude:long_name = "longitude" ;
double time(time) ;
time:units = "seconds since 1970-01-01 00:00:00.0 0:00" ;
time:reference_time = "1637193600." ;
time:reference_time_type = "3" ;
time:reference_date = "2021.11.18 00:00:00 UTC" ;
time:time_step_setting = "auto" ;
time:time_step = "21600." ;
float sample_observation(time, latitude, longitude) ;
sample_observation:units = "m" ;
sample_observation:long_name = "sample observation" ;
sample_observation:short_name = "so" ;
data:
time = _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _,
_, _, _, _, _, _, _ ;
}
Code Part:
```
void addData(netCDF::NcFile* file) {
netCDF::NcDim latDim = file->addDim(LATITUDE, LAT_SIZE);
netCDF::NcDim lonDim = file->addDim(LONGITUDE, LON_SIZE);
netCDF::NcDim timeDim = file->addDim(TIME);
std::vector<netCDF::NcDim> dims;
dims.push_back(timeDim);
dims.push_back(latDim);
dims.push_back(lonDim);
float lats[LAT_SIZE] = {-90, -89, -88, -87, -86, -85, -84, -83, -82,
-81, -80, -79, -78,
-77, -76, -75, -74, -73, -72, -71, -70, -69,
-68, -67, -66, -65, -64,
-63, -62, -61, -60, -59, -58, -57, -56, -55,
-54, -53, -52, -51, -50,
-49, -48, -47, -46, -45, -44, -43, -42, -41,
-40, -39, -38, -37, -36,
-35, -34, -33, -32, -31, -30, -29, -28, -27,
-26, -25, -24, -23, -22,
-21, -20, -19, -18, -17, -16, -15, -14, -13,
-12, -11, -10, -9, -8, -7,
-6, -5, -4, -3, -2, -1, 0, 1, 2, 3, 4, 5, 6, 7,
8, 9, 10, 11, 12, 13, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26,
27, 28, 29, 30, 31, 32,
33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44,
45, 46, 47, 48, 49, 50,
51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62,
63, 64, 65, 66, 67, 68,
69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80,
81, 82, 83, 84, 85, 86,
87, 88, 89, 90};
float lons[LON_SIZE] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13,
14, 15, 16, 17,
18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29,
30, 31, 32, 33, 34, 35,
36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47,
48, 49, 50, 51, 52, 53,
54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65,
66, 67, 68, 69, 70, 71,
72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83,
84, 85, 86, 87, 88, 89,
90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100,
101, 102, 103, 104, 105,
106, 107, 108, 109, 110, 111, 112, 113, 114,
115, 116, 117, 118, 119,
120, 121, 122, 123, 124, 125, 126, 127, 128,
129, 130, 131, 132, 133,
134, 135, 136, 137, 138, 139, 140, 141, 142,
143, 144, 145, 146, 147,
148, 149, 150, 151, 152, 153, 154, 155, 156,
157, 158, 159, 160, 161,
162, 163, 164, 165, 166, 167, 168, 169, 170,
171, 172, 173, 174, 175,
176, 177, 178, 179, 180, 181, 182, 183, 184,
185, 186, 187, 188, 189,
190, 191, 192, 193, 194, 195, 196, 197, 198,
199, 200, 201, 202, 203,
204, 205, 206, 207, 208, 209, 210, 211, 212,
213, 214, 215, 216, 217,
218, 219, 220, 221, 222, 223, 224, 225, 226,
227, 228, 229, 230, 231,
232, 233, 234, 235, 236, 237, 238, 239, 240,
241, 242, 243, 244, 245,
246, 247, 248, 249, 250, 251, 252, 253, 254,
255, 256, 257, 258, 259,
260, 261, 262, 263, 264, 265, 266, 267, 268,
269, 270, 271, 272, 273,
274, 275, 276, 277, 278, 279, 280, 281, 282,
283, 284, 285, 286, 287,
288, 289, 290, 291, 292, 293, 294, 295, 296,
297, 298, 299, 300, 301,
302, 303, 304, 305, 306, 307, 308, 309, 310,
311, 312, 313, 314, 315,
316, 317, 318, 319, 320, 321, 322, 323, 324,
325, 326, 327, 328, 329,
330, 331, 332, 333, 334, 335, 336, 337, 338,
339, 340, 341, 342, 343,
344, 345, 346, 347, 348, 349, 350, 351, 352,
353, 354, 355, 356, 357,
358, 359 };
double times[TIME_SIZE] = {1637215200, 1637236800, 1637258400,
1637280000, 1637301600,
1637323200, 1637344800, 1637366400,
1637388000, 1637409600, 1637431200,
1637452800, 1637474400, 1637496000,
1637517600, 1637539200, 1637560800,
1637582400, 1637604000, 1637625600,
1637647200, 1637668800, 1637690400,
1637712000, 1637733600, 1637755200,
1637776800, 1637798400, 1637820000};
netCDF::NcVar latVar = file->addVar(LATITUDE, netCDF::ncFloat, latDim);
latVar.putVar(lats);
netCDF::NcVar lonVar = file->addVar(LONGITUDE, netCDF::ncFloat, lonDim);
lonVar.putVar(lons);
netCDF::NcVar timeVar = file->addVar(TIME, netCDF::ncDouble, timeDim);
timeVar.putVar(times);
...
```
Any recommendations on how to set the unlimited dimension without losing
the data?
Jacob Adams
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