Dfs0 - Relative time axis

MIKE IO uses a pandas DatetimeIndex to represent the time dimension in dfs files. If the Dfs file has a relative time axis it will be converted to DatetimeIndex by using 1970-1-1 00:00:00 as start time.

import mikeio

ds = mikeio.read("../tests/testdata/eq_relative.dfs0")
ds

<mikeio.Dataset>
dims: (time:504)
time: 1970-01-01 00:00:00 - 1970-01-01 00:00:56.237000 (504 non-equidistant records)
items:
  0:  Item 1 <Undefined> (undefined)
  1:  Item 2 <Undefined> (undefined)
  2:  Item 3 <Undefined> (undefined)
  3:  Item 4 <Undefined> (undefined)
  4:  Item 5 <Undefined> (undefined)

df = ds.to_dataframe()
df.head()

	Item 1	Item 2	Item 3	Item 4	Item 5
1970-01-01 00:00:00.000	-0.006862	-0.000611	0.177047	32.484425	-304.720428
1970-01-01 00:00:00.112	-0.011746	-0.000611	0.189257	32.292774	-308.553406
1970-01-01 00:00:00.224	-0.006862	-0.000611	0.189257	32.292774	-308.553406
1970-01-01 00:00:00.335	-0.001978	0.004273	0.189257	32.292774	-300.887482
1970-01-01 00:00:00.447	0.002906	0.009157	0.177047	32.292774	-300.887482

Correcing the dataframe index by subtracting start time to get relative time axis.

df.index = (df.index - df.index[0]).total_seconds()
df.index.name = "Relative time (s)"

df.head()

	Item 1	Item 2	Item 3	Item 4	Item 5
Relative time (s)
0.000	-0.006862	-0.000611	0.177047	32.484425	-304.720428
0.112	-0.011746	-0.000611	0.189257	32.292774	-308.553406
0.224	-0.006862	-0.000611	0.189257	32.292774	-308.553406
0.335	-0.001978	0.004273	0.189257	32.292774	-300.887482
0.447	0.002906	0.009157	0.177047	32.292774	-300.887482

df['Item 5'].plot();