Re: Nonzero Min[]

• To: mathgroup at smc.vnet.net
• Subject: [mg43543] Re: Nonzero Min[]
• From: "Peter Pein" <peter1963 at totalise.co.uk>
• Date: Fri, 19 Sep 2003 03:42:12 -0400 (EDT)
• References: <bk9jgo\$t9c\$1@smc.vnet.net> <bkc0qn\$asg\$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```Oops, should have been:
Min [DeleteCases [dat, 0 | 0. ] ]

Peter

"Peter Pein" <peter1963 at totalise.co.uk> schrieb im Newsbeitrag
news:bkc0qn\$asg\$1 at smc.vnet.net...
> Petr,
> the fastest I was able to find is: Min[DeleteCases[dat,0]].
> It is 3.4 times faster than your findmin3[] (Mathematica 4.0 on Windoze).
>
> Peter
>
>
> "Petr Kujan" <kujanp at fel.cvut.cz> schrieb im Newsbeitrag
> news:bk9jgo\$t9c\$1 at smc.vnet.net...
> > 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.
> >
>
>

```

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