MathGroup Archive 2001

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: checking for a particular value in a matrix

  • To: mathgroup at
  • Subject: [mg30950] Re: checking for a particular value in a matrix
  • From: "Allan Hayes" <hay at>
  • Date: Fri, 28 Sep 2001 03:54:58 -0400 (EDT)
  • References: <9ouhbm$198$>
  • Sender: owner-wri-mathgroup at


1) oneOneQ2[mat_,r_]:= Cases[mat[[r]],1,{1},2]== {1}


oneOneQ2s[mat_,r_]:= Cases[mat[[r]],1]== {1}

The first one is likely to be quicker if you have many ones in the rows.

Please try the following

convert[a_] := Sum[a[[i]]*2^(Length[a]-i),{i,1,Length[a]}]

I am assuming that you want a to be a list.
The other change is to  use SetDelayed (:=) instead of Set(=). This
preventst the right side of the assignment from evaluaing (to zero) before
the rule is stored.

Allan Hayes
Mathematica Training and Consulting
Leicester UK
hay at
Voice: +44 (0)116 271 4198
Fax: +44 (0)870 164 0565

"Au Han Bin" <auhb3 at> wrote in message
news:9ouhbm$198$1 at
> Hi, I am a programming newbie and I need advice on how to check that a
> table or matrix , for all nonzero entries in a given row, has only one
> entry of value 1.
> i have another query on why the code below does not work, when i call
> convert{1,0,0,0} again, the results given are from an earlier question,
> e.g. {1,1} is it initialised wrongly?
> Clear[a,convert];
> convert[a___] = Sum[a[[i]]*2^(Length[a]-i),{i,1,Length[a]}]
> regards, thanks,
> joshua

  • Prev by Date: Re: FileName and Shell Command
  • Next by Date: Strange syntax errors when writing functions ?
  • Previous by thread: Re: checking for a particular value in a matrix
  • Next by thread: RE: checking for a particular value in a matrix