Re: Nonzero Min[]
- To: mathgroup at smc.vnet.net
- Subject: [mg43479] Re: Nonzero Min[]
- From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
- Date: Thu, 18 Sep 2003 05:38:41 -0400 (EDT)
- Organization: Universitaet Leipzig
- References: <bk9jgo$t9c$1@smc.vnet.net>
- Reply-to: kuska at informatik.uni-leipzig.de
- Sender: owner-wri-mathgroup at wolfram.com
Hi,
and
ZeroQ[0] = True
ZeroQ[0.] = True
ZeroQ[_] := False
findmin1[data_] := Min[data /. _?ZeroQ :> Sequence[]]
is not faster ??
Regards
Jens
Petr Kujan wrote:
>
> Hello MathGroup,
> I need function which finds nonzero minimum in the list. My
> definitions are now slower in comparison with kernel function Min[ ].
>
> findmin1[data_] := Min[data]
> findmin1[dat] // Timing (* 0.01 Second*) (* Very good time consumption
> but wrong result for me. *)
>
> It's possible shorter time consumption for this problem?
>
> (*************************************************************)
> My definition are now:
>
> (* Testing data are Integer or Real numbers (possible mixed). *)
> SeedRandom[1];
> dat = Abs[Join[Array[Random[
> Integer, {-10, 10}]&, {10^4}], Array[Random[Real, {-10, 10}]&,
> {10^4}]]];
>
> (*** 2. - Select ***)
> findmin2[data_] := Min[Select[data, Not[ZeroQ[#]]&]];
> findmin3[dat] // Timing
> (* 0.12 Second *)
>
> (*** 3. - Sort ***)
> dropfirstzeros[dat_List] := Block[{i}, i = 1;
> While[ZeroQ[dat[[i]]], i = i + 1;];
> Drop[dat, i - 1]];
> findmin2[data_] := dropfirstzeros[Sort[data]][[1]];
> findmin2[dat] // Timing
> (* 0.14 Second *)
>
> (*** 4. - Map ***)
> getnznum[list_] := Block[{i = 1},
> While[ZeroQ[list[[i]]], i++]; list[[i]]
> ];
> findmin4[data_] := Block[{minim = getnznum[data]},
> If[(# > 0) && (minim > #), minim = #] & /@ data;
> minim
> ];
> findmin4[dat] // Timing
> (* 0.26 Second *)
>
> (*** 5. - Do ***)
> getnznum[list_] := Block[{i = 1},
> While[ZeroQ[list[[i]]], i++]; list[[i]]
> ];
> findmin5[data_] := Block[{minim, p},
> minim = getnznum[data];
> Do[
> p = data[[i]];
> If[((p > 0) && (minim > p)), minim = p],
> {i, 1, Length[data]}
> ];
> minim
> ]
> findmin5[dat] // Timing
> (* 0.32 Second *)
> (*************************************************************)
>
> Thank in advance for all your help.
> Best regards,
> Petr.