python - Pandas - consecutive values must be different -



python - Pandas - consecutive values must be different -

i want subsample rows of dataframe such pairs of consecutive values in given column different, if 2 of them same, keep, say, first one.

here example

p = [1,1,2,1,3,3,2,4,3] t = range(len(p)) df = pd.dataframe({'t':t, 'p':p}) df p t 0 1 0 1 1 1 2 2 2 3 1 3 4 3 4 5 3 5 6 2 6 7 4 7 8 3 8 desireddf p t 0 1 0 2 2 2 3 1 3 4 3 4 6 2 6 7 4 7 8 3 8

in desireddf, 2 consecutive values in p column different.

how this?

>>> df[df.p != df.p.shift()] p t 0 1 0 2 2 2 3 1 3 4 3 4 6 2 6 7 4 7 8 3 8

explanation: df.p.shift() shifts entries of column p downwards row. df.p != df.p.shift() checks each entry of df.p different previous entry, returning boolean value.

this method works on columns number of consecutive entries: e.g. if there run of 3 identical values, first value in run returned.

python pandas dataframes distinct-values subsampling

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