Heh... neither did I... I gave you code for column sums! Should be easy
enough to convert...
On Tue, Jul 28, 2015 at 12:05 PM, Stefan Karpinski <ste...@karpinski.org>
wrote:
> Oh, didn't catch that you wanted row sums, but yeah, same basic idea.
>
> On Tue, Jul 28, 2015 at 12:03 PM, Tom Breloff <t...@breloff.com> wrote:
>
>> I would just write the loop explicitly:
>>
>>
>> julia> function meanpositives(mat::Matrix)
>> nc = size(mat,2)
>> sums = zeros(nc)
>> counts = zeros(nc)
>> for c in 1:nc
>> for r in 1:size(mat,1)
>> v = mat[r,c]
>> if v > 0
>> sums[c] += v
>> counts[c] += 1.0
>> end
>> end
>> end
>> Float64[(counts[i]>0 ? sums[i]/counts[i] : 0.0) for i in 1:nc]
>> end
>> meanpositives (generic function with 1 method)
>>
>> julia> x
>> 3x3 Array{Float64,2}:
>> 10.0 5.0 0.0
>> 5.0 0.0 0.0
>> 0.0 0.0 0.0
>>
>> julia> meanpositives(x)
>> 3-element Array{Float64,1}:
>> 7.5
>> 5.0
>> 0.0
>>
>>
>> On Tue, Jul 28, 2015 at 12:01 PM, Stefan Karpinski <ste...@karpinski.org>
>> wrote:
>>
>>> You mean quicker as in faster or as in easier? Using indexing is
>>> probably easiest but not fastest:
>>>
>>> julia> M = randn(5,5)
>>> 5x5 Array{Float64,2}:
>>> -1.51134 1.2331 -0.186083 0.412282 -1.13114
>>> -0.0411132 0.124684 0.377426 0.622427 -0.278162
>>> 0.788182 -0.834092 1.09506 1.45196 -0.620717
>>> 1.45856 -0.889277 -0.768049 -0.95953 -0.340098
>>> 1.69666 0.695566 0.706905 0.63089 0.958474
>>>
>>> julia> mean(M[M .> 0])
>>> 0.8751552351448673
>>>
>>>
>>> If you want the fastest, loop through the matrix and keep totals and
>>> counts:
>>>
>>> julia> function meanpos(a)
>>> t = zero(eltype(a))
>>> c = 0
>>> for x in a
>>> x > 0 || continue
>>> t += x
>>> c += 1
>>> end
>>> return t/c
>>> end
>>> meanpos (generic function with 1 method)
>>>
>>> julia> meanpos(M)
>>> 0.8751552351448673
>>>
>>>
>>> This should be fairly efficient for any non-sparse collection.
>>>
>>>
>>> On Tue, Jul 28, 2015 at 11:50 AM, Jude <judithmdela...@gmail.com> wrote:
>>>
>>>> Hi!
>>>>
>>>> Probably a quite basic question but was wondering if someone knows a quick
>>>> way to get the average of theh positive elements of a matrix, eg, If I have
>>>> an m*n matrix and want to get the average for each m so have m*1 but only
>>>> want to work with non-zero elements and ignore the zero elements and
>>>> negative elements
>>>>
>>>> I guess I could using indexing and pull out the indexes corresponding
>>>> to the positive elements but just wondering if anyone knew quicker ways!
>>>>
>>>> Thanks!
>>>>
>>>
>>>
>>
>
