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Optionally include open cycles in rainflow cycle counting #19

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Optionally include open cycles in rainflow cycle counting #19

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56 changes: 26 additions & 30 deletions fatpack/rainflow.py
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Original file line number Diff line number Diff line change
Expand Up @@ -251,13 +251,15 @@ def concatenate_reversals(reversals1, reversals2):
return np.concatenate(result)


def find_rainflow_cycles(reversals):
def find_rainflow_cycles(reversals, include_open_cycles=False):
"""Return the rainflow cycles and residue from a sequence of reversals.

Arguments
---------
reversals : 1darray
An 1D-array of reversals.
include_open_cycles : bool, optional
An optional flag to include open cycles (default is False).

Returns
-------
Expand Down Expand Up @@ -303,7 +305,7 @@ def find_rainflow_cycles(reversals):

"""

result = []
cycles_firstpass = []
residue = []
len_residue = 0
for reversal in reversals:
Expand All @@ -313,13 +315,31 @@ def find_rainflow_cycles(reversals):
S0, S1, S2, S3 = residue[-4], residue[-3], residue[-2], residue[-1]
dS1, dS2, dS3 = fabs(S1-S0), fabs(S2-S1), fabs(S3-S2)
if (dS2 <= dS1) and (dS2 <= dS3):
result += [[S1, S2]]
cycles_firstpass += [[S1, S2]]
del residue[-3]
del residue[-2]
len_residue -= 2
else:
break
return np.array(result), np.array(residue)

if include_open_cycles:
cycles_firstpass = np.array(cycles_firstpass)
processed_residue = concatenate_reversals(residue, residue)
cycles_open_sequence = find_rainflow_cycles(processed_residue)[0]
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Here is the recursive function call.

found_cycles_firstpass = len(cycles_firstpass.shape) == 2
found_cycles_open_sequence = len(cycles_open_sequence.shape) == 2
if found_cycles_firstpass and found_cycles_open_sequence:
rainflow_cycles = np.concatenate((cycles_firstpass, cycles_open_sequence))
elif found_cycles_firstpass:
rainflow_cycles = cycles_firstpass
elif found_cycles_open_sequence:
rainflow_cycles = cycles_open_sequence
else:
raise ValueError("Could not find any cycles in sequence")
else:
rainflow_cycles = cycles_firstpass

return np.array(rainflow_cycles), np.array(residue)


def find_rainflow_matrix(data_array, rowbins, colbins, return_bins=False):
Expand Down Expand Up @@ -495,19 +515,7 @@ def find_rainflow_ranges(y, k=64, return_means=False):
"""

reversals, _ = find_reversals(y, k)
cycles_firstpass, residue = find_rainflow_cycles(reversals)
processed_residue = concatenate_reversals(residue, residue)
cycles_open_sequence, _ = find_rainflow_cycles(processed_residue)
found_cycles_firstpass = len(cycles_firstpass.shape) == 2
found_cycles_open_sequence = len(cycles_open_sequence.shape) == 2
if found_cycles_firstpass and found_cycles_open_sequence:
cycles = np.concatenate((cycles_firstpass, cycles_open_sequence))
elif found_cycles_firstpass:
cycles = cycles_firstpass
elif found_cycles_open_sequence:
cycles = cycles_open_sequence
else:
raise ValueError("Could not find any cycles in sequence")
cycles, residue = find_rainflow_cycles(reversals, include_open_cycles=True)
ranges = np.abs(cycles[:, 1] - cycles[:, 0])
if return_means:
means = 0.5 * (cycles[:, 0] + cycles[:, 1])
Expand Down Expand Up @@ -562,19 +570,7 @@ def find_rainflow_ranges_strict(y, k=64, return_means=False):
"""

reversals, _ = find_reversals_strict(y, k)
cycles_firstpass, residue = find_rainflow_cycles(reversals)
processed_residue = concatenate_reversals(residue, residue)
cycles_open_sequence, _ = find_rainflow_cycles(processed_residue)
found_cycles_firstpass = len(cycles_firstpass.shape) == 2
found_cycles_open_sequence = len(cycles_open_sequence.shape) == 2
if found_cycles_firstpass and found_cycles_open_sequence:
cycles = np.concatenate((cycles_firstpass, cycles_open_sequence))
elif found_cycles_firstpass:
cycles = cycles_firstpass
elif found_cycles_open_sequence:
cycles = cycles_open_sequence
else:
raise ValueError("Could not find any cycles in sequence")
cycles, residue = find_rainflow_cycles(reversals, include_open_cycles=True)
ranges = np.abs(cycles[:, 1] - cycles[:, 0])
if return_means:
means = 0.5 * (cycles[:, 0] + cycles[:, 1])
Expand Down