Cannot find variable with ncread

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Eki
Eki on 2 Jul 2022
Commented: dpb on 2 Jul 2022
Hi, I am trying to extract data from an .nc file using the below code:
ncdisp('Marconi_v02_map_5years.nc')
The output that is given is:
Source:
C:\Users\ekili\Documents\Studie\2021-2022\Kwartiel 4\Building with Nature\Project\MarconiModel_2022\Plots\Marconi_v02_map_5years.nc
Format:
classic
Global Attributes:
institution = 'Deltares'
references = 'http://www.deltares.nl'
source = 'D-Flow FM 1.1.192.50903. Model:'
history = 'Created on 2022-07-01T19:54:36+0200, D-Flow FM'
date_created = '2022-07-01T19:54:36+0200'
date_modified = '2022-07-01T19:54:36+0200'
Conventions = 'CF-1.6 UGRID-1.0/Deltares-0.8'
Dimensions:
nmesh2d_node = 9794
nmesh2d_edge = 20346
nmesh2d_Two = 2
nmesh2d_face = 10553
max_nmesh2d_face_nodes = 4
time = 241 (UNLIMITED)
Variables:
mesh2d
Size: 1x1
Dimensions:
Datatype: int32
Attributes:
cf_role = 'mesh_topology'
long_name = 'Topology data of 2D network'
topology_dimension = 2
node_coordinates = 'mesh2d_node_x mesh2d_node_y'
node_dimension = 'nmesh2d_node'
max_face_nodes_dimension = 'max_nmesh2d_face_nodes'
edge_node_connectivity = 'mesh2d_edge_nodes'
edge_dimension = 'nmesh2d_edge'
edge_coordinates = 'mesh2d_edge_x mesh2d_edge_y'
face_node_connectivity = 'mesh2d_face_nodes'
face_dimension = 'nmesh2d_face'
face_coordinates = 'mesh2d_face_x mesh2d_face_y'
projected_coordinate_system
Size: 1x1
Dimensions:
Datatype: int32
Attributes:
name = 'Unknown projected'
epsg = 0
grid_mapping_name = 'Unknown projected'
longitude_of_prime_meridian = 0
semi_major_axis = 6378137
semi_minor_axis = 6356752.3142
inverse_flattening = 298.2572
EPSG_code = 'EPSG:0'
value = 'value is equal to EPSG code'
mesh2d_node_x
Size: 9794x1
Dimensions: nmesh2d_node
Datatype: double
Attributes:
units = 'm'
standard_name = 'projection_x_coordinate'
long_name = 'x-coordinate of mesh nodes'
mesh = 'mesh2d'
location = 'node'
mesh2d_node_y
Size: 9794x1
Dimensions: nmesh2d_node
Datatype: double
Attributes:
units = 'm'
standard_name = 'projection_y_coordinate'
long_name = 'y-coordinate of mesh nodes'
mesh = 'mesh2d'
location = 'node'
mesh2d_node_z
Size: 9794x1
Dimensions: nmesh2d_node
Datatype: double
Attributes:
mesh = 'mesh2d'
location = 'node'
coordinates = 'mesh2d_node_x mesh2d_node_y'
standard_name = 'altitude'
long_name = 'z-coordinate of mesh nodes'
units = 'm'
grid_mapping = ''
_FillValue = -999
mesh2d_edge_nodes
Size: 2x20346
Dimensions: nmesh2d_Two,nmesh2d_edge
Datatype: int32
Attributes:
cf_role = 'edge_node_connectivity'
mesh = 'mesh2d'
location = 'edge'
long_name = 'Mapping from every edge to the two nodes that it connects'
start_index = 1
_FillValue = -999
mesh2d_edge_x
Size: 20346x1
Dimensions: nmesh2d_edge
Datatype: double
Attributes:
units = 'm'
standard_name = 'projection_x_coordinate'
long_name = 'characteristic x-coordinate of the mesh edge (e.g., midpoint)'
mesh = 'mesh2d'
location = 'edge'
bounds = 'mesh2d_edge_x_bnd'
mesh2d_edge_y
Size: 20346x1
Dimensions: nmesh2d_edge
Datatype: double
Attributes:
units = 'm'
standard_name = 'projection_y_coordinate'
long_name = 'characteristic y-coordinate of the mesh edge (e.g., midpoint)'
mesh = 'mesh2d'
location = 'edge'
bounds = 'mesh2d_edge_y_bnd'
mesh2d_edge_x_bnd
Size: 2x20346
Dimensions: nmesh2d_Two,nmesh2d_edge
Datatype: double
Attributes:
units = 'm'
standard_name = 'projection_x_coordinate'
long_name = 'x-coordinate bounds of 2D mesh edge (i.e. end point coordinates)'
mesh = 'mesh2d'
location = 'edge'
mesh2d_edge_y_bnd
Size: 2x20346
Dimensions: nmesh2d_Two,nmesh2d_edge
Datatype: double
Attributes:
units = 'm'
standard_name = 'projection_y_coordinate'
long_name = 'y-coordinate bounds of 2D mesh edge (i.e. end point coordinates)'
mesh = 'mesh2d'
location = 'edge'
mesh2d_face_nodes
Size: 4x10553
Dimensions: max_nmesh2d_face_nodes,nmesh2d_face
Datatype: int32
Attributes:
cf_role = 'face_node_connectivity'
mesh = 'mesh2d'
location = 'face'
long_name = 'Mapping from every face to its corner nodes (counterclockwise)'
start_index = 1
_FillValue = -999
mesh2d_face_x
Size: 10553x1
Dimensions: nmesh2d_face
Datatype: double
Attributes:
units = 'm'
standard_name = 'projection_x_coordinate'
long_name = 'Characteristic x-coordinate of mesh face'
mesh = 'mesh2d'
location = 'face'
bounds = 'mesh2d_face_x_bnd'
mesh2d_face_y
Size: 10553x1
Dimensions: nmesh2d_face
Datatype: double
Attributes:
units = 'm'
standard_name = 'projection_y_coordinate'
long_name = 'Characteristic y-coordinate of mesh face'
mesh = 'mesh2d'
location = 'face'
bounds = 'mesh2d_face_y_bnd'
mesh2d_face_x_bnd
Size: 4x10553
Dimensions: max_nmesh2d_face_nodes,nmesh2d_face
Datatype: double
Attributes:
units = 'm'
standard_name = 'projection_x_coordinate'
long_name = 'x-coordinate bounds of 2D mesh face (i.e. corner coordinates)'
mesh = 'mesh2d'
location = 'face'
_FillValue = -999
mesh2d_face_y_bnd
Size: 4x10553
Dimensions: max_nmesh2d_face_nodes,nmesh2d_face
Datatype: double
Attributes:
units = 'm'
standard_name = 'projection_y_coordinate'
long_name = 'y-coordinate bounds of 2D mesh face (i.e. corner coordinates)'
mesh = 'mesh2d'
location = 'face'
_FillValue = -999
mesh2d_edge_type
Size: 20346x1
Dimensions: nmesh2d_edge
Datatype: int32
Attributes:
mesh = 'mesh2d'
location = 'edge'
coordinates = 'mesh2d_edge_x mesh2d_edge_y'
cell_methods = 'nmesh2d_edge: mean'
standard_name = ''
long_name = 'edge type (relation between edge and flow geometry)'
units = ''
_FillValue = -999
flag_values = [0 1 2 3]
flag_meanings = 'internal_closed internal boundary boundary_closed'
mesh2d_flowelem_ba
Size: 10553x1
Dimensions: nmesh2d_face
Datatype: double
Attributes:
mesh = 'mesh2d'
location = 'face'
coordinates = 'mesh2d_face_x mesh2d_face_y'
cell_methods = 'nmesh2d_face: mean'
standard_name = 'cell_area'
long_name = ''
units = 'm2'
grid_mapping = ''
_FillValue = -999
mesh2d_flowelem_bl
Size: 10553x1
Dimensions: nmesh2d_face
Datatype: double
Attributes:
mesh = 'mesh2d'
location = 'face'
coordinates = 'mesh2d_face_x mesh2d_face_y'
cell_methods = 'nmesh2d_face: mean'
standard_name = 'altitude'
long_name = 'flow element center bedlevel (bl)'
units = 'm'
grid_mapping = ''
_FillValue = -999
time
Size: 241x1
Dimensions: time
Datatype: double
Attributes:
standard_name = 'Time'
units = 'seconds since 2012-01-01 00:00:00'
timestep
Size: 241x1
Dimensions: time
Datatype: double
Attributes:
long_name = 'Latest computational timestep size in each output interval'
units = 's'
mesh2d_Numlimdt
Size: 10553x241
Dimensions: nmesh2d_face,time
Datatype: double
Attributes:
mesh = 'mesh2d'
location = 'face'
coordinates = 'mesh2d_face_x mesh2d_face_y'
cell_methods = 'nmesh2d_face: mean'
standard_name = ''
long_name = 'Number of times flow element was Courant limiting'
units = '1'
grid_mapping = ''
_FillValue = -999
mesh2d_s1
Size: 10553x241
Dimensions: nmesh2d_face,time
Datatype: double
Attributes:
mesh = 'mesh2d'
location = 'face'
coordinates = 'mesh2d_face_x mesh2d_face_y'
cell_methods = 'nmesh2d_face: mean'
standard_name = 'sea_surface_height'
long_name = 'Water level'
units = 'm'
grid_mapping = ''
_FillValue = -999
mesh2d_waterdepth
Size: 10553x241
Dimensions: nmesh2d_face,time
Datatype: double
Attributes:
mesh = 'mesh2d'
location = 'face'
coordinates = 'mesh2d_face_x mesh2d_face_y'
cell_methods = 'nmesh2d_face: mean'
standard_name = 'sea_floor_depth_below_sea_surface'
long_name = 'Water depth at pressure points'
units = 'm'
grid_mapping = ''
_FillValue = -999
mesh2d_s0
Size: 10553x241
Dimensions: nmesh2d_face,time
Datatype: double
Attributes:
mesh = 'mesh2d'
location = 'face'
coordinates = 'mesh2d_face_x mesh2d_face_y'
cell_methods = 'nmesh2d_face: mean'
standard_name = 'sea_surface_height'
long_name = 'Water level on previous timestep'
units = 'm'
grid_mapping = ''
_FillValue = -999
mesh2d_u1
Size: 20346x241
Dimensions: nmesh2d_edge,time
Datatype: double
Attributes:
mesh = 'mesh2d'
location = 'edge'
coordinates = 'mesh2d_edge_x mesh2d_edge_y'
cell_methods = 'nmesh2d_edge: mean'
standard_name = ''
long_name = 'Normal velocity at velocity point'
units = 'm s-1'
grid_mapping = ''
_FillValue = -999
comment = 'Positive direction is from first to second neighbouring face (flow element).'
mesh2d_u0
Size: 20346x241
Dimensions: nmesh2d_edge,time
Datatype: double
Attributes:
mesh = 'mesh2d'
location = 'edge'
coordinates = 'mesh2d_edge_x mesh2d_edge_y'
cell_methods = 'nmesh2d_edge: mean'
standard_name = ''
long_name = 'Normal velocity at velocity point at previous time step'
units = 'm s-1'
grid_mapping = ''
_FillValue = -999
comment = 'Positive direction is from first to second neighbouring face (flow element).'
mesh2d_ucx
Size: 10553x241
Dimensions: nmesh2d_face,time
Datatype: double
Attributes:
mesh = 'mesh2d'
location = 'face'
coordinates = 'mesh2d_face_x mesh2d_face_y'
cell_methods = 'nmesh2d_face: mean'
standard_name = 'sea_water_x_velocity'
long_name = 'Flow element center velocity vector, x-component'
units = 'm s-1'
grid_mapping = ''
_FillValue = -999
mesh2d_ucy
Size: 10553x241
Dimensions: nmesh2d_face,time
Datatype: double
Attributes:
mesh = 'mesh2d'
location = 'face'
coordinates = 'mesh2d_face_x mesh2d_face_y'
cell_methods = 'nmesh2d_face: mean'
standard_name = 'sea_water_y_velocity'
long_name = 'Flow element center velocity vector, y-component'
units = 'm s-1'
grid_mapping = ''
_FillValue = -999
mesh2d_q1
Size: 20346x241
Dimensions: nmesh2d_edge,time
Datatype: double
Attributes:
mesh = 'mesh2d'
location = 'edge'
coordinates = 'mesh2d_edge_x mesh2d_edge_y'
cell_methods = 'nmesh2d_edge: mean'
standard_name = 'discharge'
long_name = 'Discharge through flow link at current time'
units = 'm3 s-1'
grid_mapping = ''
_FillValue = -999
comment = 'Positive direction is from first to second neighbouring face (flow element).'
mesh2d_taus
Size: 10553x241
Dimensions: nmesh2d_face,time
Datatype: double
Attributes:
mesh = 'mesh2d'
location = 'face'
coordinates = 'mesh2d_face_x mesh2d_face_y'
cell_methods = 'nmesh2d_face: mean'
standard_name = ''
long_name = 'Total bed shear stress'
units = 'N m-2'
grid_mapping = ''
_FillValue = -999
mesh2d_czs
Size: 10553x241
Dimensions: nmesh2d_face,time
Datatype: double
Attributes:
mesh = 'mesh2d'
location = 'face'
coordinates = 'mesh2d_face_x mesh2d_face_y'
cell_methods = 'nmesh2d_face: mean'
standard_name = ''
long_name = 'Chezy roughness'
units = 'm0.5s-1'
grid_mapping = ''
_FillValue = -999
Where from above I want to extraxt 'mesh2d_taus'.
tau = ncread('Marconi_v02_his_5years.nc','mesh2d_taus')
Which gives the following error:
Error using internal.matlab.imagesci.nc/getGroupAndVarid
Could not find variable or group 'mesh2d_taus' in file.
Error in internal.matlab.imagesci.nc/read (line 632)
[gid, varid] = getGroupAndVarid(this, location);
Error in ncread (line 74)
vardata = ncObj.read(varName, varargin{:});
Error in plotthindams (line 5)
tau = ncread('Marconi_v02_his_5years.nc','mesh2d_taus')
Does anyone know how to extract the variable?
  1 Comment
dpb
dpb on 2 Jul 2022
Can you read any variable?
We'd have to have the file to try out anything here...attach it w/ paperclip icon.

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Answers (1)

Ayush Kumar Jaiswal
Ayush Kumar Jaiswal on 2 Jul 2022
You are using different file name to retrieve contents. It should instead be:
tau = ncread('Marconi_v02_map_5years.nc','mesh2d_taus')

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