Dfsu - Read

import mikeio

filename = "../tests/testdata/HD2D.dfsu"
ds = mikeio.read(filename)
ds

<mikeio.Dataset>
dims: (time:9, element:884)
time: 1985-08-06 07:00:00 - 1985-08-07 03:00:00 (9 records)
geometry: Dfsu2D (884 elements, 529 nodes)
items:
  0:  Surface elevation <Surface Elevation> (meter)
  1:  U velocity <u velocity component> (meter per sec)
  2:  V velocity <v velocity component> (meter per sec)
  3:  Current speed <Current Speed> (meter per sec)

# to read specific variables
ds = mikeio.read(filename, items=["Surface elevation","Current speed"]) 
ds

<mikeio.Dataset>
dims: (time:9, element:884)
time: 1985-08-06 07:00:00 - 1985-08-07 03:00:00 (9 records)
geometry: Dfsu2D (884 elements, 529 nodes)
items:
  0:  Surface elevation <Surface Elevation> (meter)
  1:  Current speed <Current Speed> (meter per sec)

ds.describe()

	Surface elevation	Current speed
count	7956.000000	7956.000000
mean	0.034152	0.073658
std	0.534890	0.119606
min	-0.758378	0.000082
25%	-0.579662	0.029917
50%	0.101636	0.046848
75%	0.462013	0.070259
max	1.172707	1.714988

Filter in space to the element at our POI, (discrete values, no interpolation)

ds.sel(x=606200, y=6905480)

<mikeio.Dataset>
dims: (time:9)
time: 1985-08-06 07:00:00 - 1985-08-07 03:00:00 (9 records)
geometry: GeometryPoint2D(x=606202.7806372638, y=6905474.639383219)
items:
  0:  Surface elevation <Surface Elevation> (meter)
  1:  Current speed <Current Speed> (meter per sec)

Interpolate in space to the location of our POI

ds.interp(x=606200, y=6905480)

<mikeio.Dataset>
dims: (time:9)
time: 1985-08-06 07:00:00 - 1985-08-07 03:00:00 (9 records)
geometry: GeometryPoint2D(x=606200, y=6905480)
items:
  0:  Surface elevation <Surface Elevation> (meter)
  1:  Current speed <Current Speed> (meter per sec)

ds.interp(x=606200, y=6905480).Surface_elevation.plot();

Convert to a dataframe.

df = ds.sel(x=606200, y=6905480).to_dataframe()
df.head()

	Surface elevation	Current speed
1985-08-06 07:00:00	0.459460	0.009572
1985-08-06 09:30:00	0.806965	0.011064
1985-08-06 12:00:00	0.100285	0.017169
1985-08-06 14:30:00	-0.727009	0.014452
1985-08-06 17:00:00	-0.579541	0.007349

df.plot();

Other ways to subset data

Assume that we interested in these 3 points only

pt1 = (606200, 6905480)
pt2 = (606300, 6905410)
pt3 = (606400, 6905520)
pts_x = [pt1[0], pt2[0], pt3[0]]
pts_y = [pt1[1], pt2[1], pt3[1]]
elem_ids = ds.geometry.find_index(pts_x, pts_y)

We can use these element ids either when we select the data from the complete dataset using the method isel() as shown above or already when we read the data from file (particular useful for files larger than memory)

ds_pts = mikeio.read(filename, elements=elem_ids)
ds_pts

<mikeio.Dataset>
dims: (time:9, element:3)
time: 1985-08-06 07:00:00 - 1985-08-07 03:00:00 (9 records)
geometry: Dfsu2D (3 elements, 7 nodes)
items:
  0:  Surface elevation <Surface Elevation> (meter)
  1:  U velocity <u velocity component> (meter per sec)
  2:  V velocity <v velocity component> (meter per sec)
  3:  Current speed <Current Speed> (meter per sec)

Create a new dfsu file

Subset of items
Renamed variables

First inspect the source file:

ds = mikeio.read("../tests/testdata/HD2D.dfsu")
ds

<mikeio.Dataset>
dims: (time:9, element:884)
time: 1985-08-06 07:00:00 - 1985-08-07 03:00:00 (9 records)
geometry: Dfsu2D (884 elements, 529 nodes)
items:
  0:  Surface elevation <Surface Elevation> (meter)
  1:  U velocity <u velocity component> (meter per sec)
  2:  V velocity <v velocity component> (meter per sec)
  3:  Current speed <Current Speed> (meter per sec)

outfilename2 = "HD2D_selected.dfsu"

newds = ds[["U velocity", "V velocity"]].rename({'U velocity': 'eastward_sea_water_velocity',
                                                 'V velocity': 'northward_sea_water_velocity'})
newds

<mikeio.Dataset>
dims: (time:9, element:884)
time: 1985-08-06 07:00:00 - 1985-08-07 03:00:00 (9 records)
geometry: Dfsu2D (884 elements, 529 nodes)
items:
  0:  eastward_sea_water_velocity <u velocity component> (meter per sec)
  1:  northward_sea_water_velocity <v velocity component> (meter per sec)

newds.to_dfs(outfilename2)

Read the newly created file to verify the contents.

newds2 = mikeio.read(outfilename2)
newds2

<mikeio.Dataset>
dims: (time:9, element:884)
time: 1985-08-06 07:00:00 - 1985-08-07 03:00:00 (9 records)
geometry: Dfsu2D (884 elements, 529 nodes)
items:
  0:  eastward_sea_water_velocity <u velocity component> (meter per sec)
  1:  northward_sea_water_velocity <v velocity component> (meter per sec)

Write mesh from dfsu file

Don’t you have the original mesh? No problem - you can re-create it from the dfsu file…

outmesh = 'mesh_from_HD2D.mesh'
ds.geometry.to_mesh(outmesh)

Clean up

import os
os.remove(outfilename2)
os.remove(outmesh)