many thanks, vcat() is indeed the best way to reassemble the output of map!
On Tuesday, December 2, 2014 2:10:50 AM UTC+13, David van Leeuwen wrote:
>
> Hi Mike,
>
> One way of obtaining what you want, using your own construction, is:
>
> *vcat(map(row->a[row,:]+1, 1:size(a)[1])...)*
>
> another way would be to use mapslices(), or write a loop, or use matrix
> calculations, all depending a bit on what your operation on the row is.
> (It may be faster to access the data in the matrix by column, so you might
> want to reorganize the data in that case.
>
> ---david
>
> On Sunday, November 30, 2014 11:11:38 PM UTC+1, Michael Mayo wrote:
>>
>> Hi,
>>
>> How do I use map or pmap in Julia to apply a function each row of a 2D
>> matrix and get back a 2D matrix with each row appropriately updated?
>> Currently, map returns an array of 1D arrays instead of a 2D array, e.g.:
>>
>> *julia> **a=rand(5,3)*
>>
>> *5x3 Array{Float64,2}:*
>>
>> * 0.0970387 0.944568 0.589086 *
>>
>> * 0.477571 0.916078 0.0674227*
>>
>> * 0.424044 0.827748 0.49385 *
>>
>> * 0.691055 0.0370019 0.845552 *
>>
>> * 0.686033 0.812021 0.222669 *
>>
>>
>> *julia> **map(row->a[row,:]+1, 1:size(a)[1])*
>>
>> *5-element Array{Array{Float64,2},1}:*
>>
>> * 1x3 Array{Float64,2}:*
>>
>> * 1.09704 1.94457 1.58909*
>>
>> * 1x3 Array{Float64,2}:*
>>
>> * 1.47757 1.91608 1.06742*
>>
>> * 1x3 Array{Float64,2}:*
>>
>> * 1.42404 1.82775 1.49385*
>>
>> * 1x3 Array{Float64,2}:*
>>
>> * 1.69106 1.037 1.84555 *
>>
>> * 1x3 Array{Float64,2}:*
>>
>> * 1.68603 1.81202 1.22267*
>>
>>
>> Although I could probably post-process the output of map back into a 2D
>> array, is there is a more elegant way of doing it?
>>
>>
>> Mike
>>
>
