linalg:row

(linalg:row array index)

Returns the axis-0 slice index of array with axis 0 dropped (numpy's x[i] integer indexing), as a fresh array of the input's width: a matrix yields the row vector, a rank-4 batch yields the rank-3 sample. The index value is truncated to an integer.

This is the one-slice sibling of linalg:take-rows, which keeps axis 0 (numpy's x[[i]], so a matrix stays a (1 n) matrix). Use linalg:row wherever numpy writes x[i] -- feeding one image of a batch to a forward pass, for instance -- and aref to read a single element. array must have rank >= 2; on a vector linalg:row signals an error, since (aref v i) already returns the element.