Re: [julia-users] Find the indice of the element with the nearest value of a float in an array

On Sunday, April 10, 2016 09:03:06 AM Fred wrote: > A huge size difference ! I have to read my array from data file so I > suppose it is like Y and X is only for simulations ? There turn out to be many situations in which you can take shortcuts if you know the values are sorted in increasing

Re: [julia-users] Find the indice of the element with the nearest value of a float in an array

A huge size difference ! I have to read my array from data file so I suppose it is like Y and X is only for simulations ? Le dimanche 10 avril 2016 17:50:02 UTC+2, Tim Holy a écrit : > > Just FYI: > > julia> x = 1:0.1:100 > 1.0:0.1:1.0e6 > > julia> y = collect(x); # this is the same as y

Re: [julia-users] Find the indice of the element with the nearest value of a float in an array

Just FYI: julia> x = 1:0.1:100 1.0:0.1:1.0e6 julia> y = collect(x); # this is the same as y = [x;] julia> sizeof(x) 32 julia> sizeof(y) 7928 --Tim On Sunday, April 10, 2016 07:26:06 AM Fred wrote: > Maybe my array is too small to see a difference, but if I increase the size > I will

Re: [julia-users] Find the indice of the element with the nearest value of a float in an array

Maybe my array is too small to see a difference, but if I increase the size I will lack of RAM ;) julia> x = 1:0.1:100 1.0:0.1:1.0e6 julia> @time searchsorted(x, 8.22) 0.045590 seconds (33.21 k allocations: 1.535 MB) 74:73 julia> @time searchsorted(x, 8.22) 0.05 seconds (8

Re: [julia-users] Find the indice of the element with the nearest value of a float in an array

Even better: get rid of the brackets around 1:0.1:10, and you'll be that much more impressed. --Tim On Sunday, April 10, 2016 07:16:16 AM Fred wrote: > Hi, > > I post here my best solution taking advantage that the array is sorted. I > expected to be a lot much faster than other solutions,

Re: [julia-users] Find the indice of the element with the nearest value of a float in an array

Hi, I post here my best solution taking advantage that the array is sorted. I expected that solution to be a lot much faster than other solutions, but not really. Indeed I am very impressed by the speed of searchsorted : x = [1:0.1:100] val = 8.22 function dicotomy(x, val) a =

Re: [julia-users] Find the indice of the element with the nearest value of a float in an array

Hi, I post here my best solution taking advantage that the array is sorted. I expected to be a lot much faster than other solutions, but not really. I am very impressed by the speed of searchsorted : x = [1:0.1:100] val = 8.22 function dicotomy(x, val) a = start(eachindex(x)) b =

Re: [julia-users] Find the indice of the element with the nearest value of a float in an array

On Sun, 2016-04-10 at 15:24, Fred wrote: > That's true ! But why a loop is faster in a function ? :) Check out: http://docs.julialang.org/en/release-0.4/manual/performance-tips/#avoid-global-variables >> >> I seem to recall that your example loop was not in a

Re: [julia-users] Find the indice of the element with the nearest value of a float in an array

That's true ! But why a loop is faster in a function ? :) > > I seem to recall that your example loop was not in a function(?) If so, > that makes it lots slower. > >

Re: [julia-users] Find the indice of the element with the nearest value of a float in an array

> I tested my loop monre than 2 times as it is written in my post and I have > always the same results. The function Tim Holy posted is much faster, I > posted the results above :) I seem to recall that your example loop was not in a function(?) If so, that makes it lots slower. >> Probably

Re: [julia-users] Find the indice of the element with the nearest value of a float in an array

I tested my loop monre than 2 times as it is written in my post and I have always the same results. The function Tim Holy posted is much faster, I posted the results above :) > Probably you are doing this wrong; it shouldn't be allocating so much > memory. Is your loop using global

Re: [julia-users] Find the indice of the element with the nearest value of a float in an array

On Sunday, April 10, 2016 at 8:30:48 AM UTC-4, Fred wrote: > > my loop solution : > 0.000419 seconds (547 allocations: 708.797 KB) > 0.02135 -> 73 > Probably you are doing this wrong; it shouldn't be allocating so much memory. Is your loop using global variables? Did you

Re: [julia-users] Find the indice of the element with the nearest value of a float in an array

Thank you very much Mauro ! searchsorted is the simplest solution and one of the fastest but it gives two indices so another comparison is needed to find the closest value : @time searchsorted(x, 8.22) 0.04 seconds (7 allocations: 240 bytes) 74:73 abs(x[73] - 8.22) > abs(x[74] - 8.22)

Re: [julia-users] Find the indice of the element with the nearest value of a float in an array

Thank you very much ! I give you the results : my loop solution : 0.000419 seconds (547 allocations: 708.797 KB) 0.02135 -> 73 @time closest_index(x,8.22) 0.03 seconds (4 allocations: 160 bytes) 73 @time for (i,x) in enumerate(array)... 0.000181 seconds (821 allocations:

Re: [julia-users] Find the indice of the element with the nearest value of a float in an array

If your array is sorted, as your example suggests, there maybe faster methods, binary search comes to mind (implemented in searchsorted). Also, if the array is unsorted but you need to look up many values, it might be worth sorting it first. Mauro On Sun, 2016-04-10 at 13:40, Fred

Re: [julia-users] Find the indice of the element with the nearest value of a float in an array

Fred Yes, the fastest way is a loop. (It might be possible to extend e.g. `minimum` by a "predicate" argument, but that would require a change to the base library.) You would write the loop slightly differently, though: ```Julia mini = 0 minx = 0.0 mindx = typemax(Float64) for (i,x) in

Re: [julia-users] Find the indice of the element with the nearest value of a float in an array

indmin(abs(x-val)) is easy and pretty good, but it does create two temporaries. Faster would be function closest_index(x, val) ibest = start(eachindex(x)) dxbest = abs(x[ibest]-val) for I in eachindex(x) dx = abs(x[I]-val) if dx < dxbest dxbest = dx

[julia-users] Find the indice of the element with the nearest value of a float in an array

Hi, I am looking for the most efficient (fastest) way to find the indice of the element with the nearest value of a float in an array. x = [1:0.1:10] julia> x 91-element Array{Float64,1}: 1.0 1.1 1.2 1.3 1.4 ⋮ 9.4 9.5 9.6 9.7 9.8 9.9 10.0 It is very easy to find the

[julia-users] find source location for type definition

Is there an equivalent of @edit function(arg1, ...) for type definitions? @edit is so nice in Emacs. Currently I am using M-x find-grep-dired RET \(type\|immutable\) Foo but something built-in for Julia would be very convenient. Best, Tamas

[julia-users] Find

`x .> 3` is a bit-array. The function form, which is probably what fits, is `x->x.>3` (the back-ticks are for quotation, not part of the code).

[julia-users] Find

when trying x=[0,1,3,4,6,1] find(x.>3,x) I always get the error: ERROR: MethodError: `find` has no method matching find(::BitArray{1}, ::Array{Int64,1}) Closest candidates are: find(::Function, ::AbstractArray{T,N}) find(::BitArray{N})

[julia-users] find element in sorted list

What is the best way of telling whether an element `x` is present in a sorted list `a`? Using `searchsortedlist`, I also need to check that the element is present in the list. This is what I do function isinsortedlist(a, x) n = searchsortedfirst(a, x) n <= length(a) && a[n] == x end

Re: [julia-users] find element in sorted list

On Sat, Nov 7, 2015 at 4:34 PM, Milan Bouchet-Valat wrote: > Le samedi 07 novembre 2015 à 06:37 -0800, Michele Zaffalon a écrit : > > What is the best way of telling whether an element `x` is present in > > a sorted list `a`? > > > > Using `searchsortedlist`, I also need to

[julia-users] Find linearly independent subset within a set of vectors without constructing a matrix

Given a set of vectors v1, , vn, I'd like to construct a matrix where columns correspond to a linearly independent subset of these vectors. Currenly, I form the matrix hcat(v1, ..., vn), use qrfact!() on it, check the diagonal of the :R matrix and construct a new matrix as hcat(vj,...) I'm

Re: [julia-users] Find sequence in array?

Le vendredi 11 septembre 2015 à 16:03 -0700, cormull...@mac.com a écrit : > Is there a Julia function/method to find the location(s) of a > sequence of elements in a 1-D array? > > With strings, you can do: > > search("longstring", "str") > > 5:7 > > so with arrays it would hopefully

Re: [julia-users] Find sequence in array?

Hi Milan - thanks for the clues! I found `Base._searchindex`, which work for integers: julia> a = rand(1:10, 100); julia> Base._searchindex(a, [19272, 52257], 1) 86 It's pretty quick, too.

[julia-users] Find sequence in array?

Is there a Julia function/method to find the location(s) of a sequence of elements in a 1-D array? With strings, you can do: search("longstring", "str") 5:7 so with arrays it would hopefully be something like: searcharray( [1, 3, 5, 7, 9, 11, 13], [5, 7, 9]) 3:5

Re: [julia-users] find function in sparse matrix

Le jeudi 11 septembre 2014 à 20:12 -0700, i.pallikarakis...@alumni.lboro.ac.uk a écrit : Hi everyone, I am new to Julia and just upgraded from 0.2.1 to 0.3.0 and found the following issue : find function is no longer working on sparse matrices. For example A=speye(Bool,10)

[julia-users] find function in sparse matrix

Hi everyone, I am new to Julia and just upgraded from 0.2.1 to 0.3.0 and found the following issue : find function is no longer working on sparse matrices. For example A=speye(Bool,10) find(x-x==true,A) -0-element Array{Int64,1} find(x-x==true,full(A)) -10-element Array{Int64,1}: 1 12 23

[julia-users] find nearest non-zero element in matrix

Hi julia-users, I am looking for a function that takes a two-dimensional matrix and a set of matrix indices as inputs and spits out the nearest non-zero element in taxicab distance over the matrix index. I am asking for your advice because this function needs to be very fast as I have to do

Re: [julia-users] find if a pointer is NULL

testing against C_NULL is probably the easiest way: p == C_NULL On Sat, Jun 14, 2014 at 10:39 PM, J Luis jmfl...@gmail.com wrote: How do I test if a pointer is NULL? (did search the docs but couldn't find and answer) and BTW, I can't get this one either docs: pointer(*type*, *int*)