larray.Array.roll

Array.roll(axis=None, n=1) → Array[source]

Roll the cells of the array n-times to the right along axis. Cells which would be pushed “outside of the axis” are reintroduced on the opposite side of the axis.

Parameters

axisint, str or Axis, optional: Axis along which to roll. Defaults to None (all axes).
nint or Array, optional: Number of positions to roll. Defaults to 1. Use a negative integers to roll left. If n is an Array the number of positions rolled can vary along the axes of n.

Returns

Array

See also

Array.shift: cells which are pushed “outside of the axis” are dropped instead of being reintroduced on the opposite side of the axis.

Examples

>>> arr = ndtest('sex=M,F;year=2019..2021')
>>> arr
sex\year  2019  2020  2021
       M     0     1     2
       F     3     4     5
>>> arr.roll('year')
sex\year  2019  2020  2021
       M     2     0     1
       F     5     3     4

One can also roll by a different amount depending on another axis

>>> # let us roll by 1 for men and by 2 for women
>>> n = sequence(arr.sex, initial=1)
>>> n
sex  M  F
     1  2
>>> arr.roll('year', n)
sex\year  2019  2020  2021
       M     2     0     1
       F     4     5     3