Have a look at the permute! function in julia:
@less permute!([1,2], [1,2])
Modifying it to
function permute!!{T<:Integer}(a, i, p::AbstractVector{T})
count = 0
start = 0
while count < length(a)
ptr = start = findnext(p, start+1)
temp = a[i,start]
next = p[start]
count += 1
while next != start
a[i,ptr] = a[i,next]
p[ptr] = 0
ptr = next
next = p[next]
count += 1
end
a[i,ptr] = temp
p[ptr] = 0
end
a
end
should work (untested). Note that permuting a column should be faster
though as julia matrices are column-major.
On Wed, 2015-03-11 at 13:49, Davide Lasagna <[email protected]> wrote:
> Hi,
>
>
> permute!(v, p) permutes the elements of v according to the permutation
> vector p.
>
> Is there any equivalent built in function for permuting rows of a matrix?
> Given the memory layout of julia matrices it should not be too difficult to
> have a similar function for matrices as well.
>
> Thanks,
>
> Davide
