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MathGroup Archive 2007

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Re: normalize a table

  • To: mathgroup at smc.vnet.net
  • Subject: [mg72792] Re: normalize a table
  • From: Peter Pein <petsie at dordos.net>
  • Date: Sat, 20 Jan 2007 02:44:31 -0500 (EST)
  • References: <eopmgk$rr4$1@smc.vnet.net>

Ruth schrieb:
> Hi,
> 
> I want to do something really simple, which is take a table made of 
> pairs and normalize the first number in each pair by dividing by the 
> largest.
> 
> For instance, I want to transform this list
> 
> {{1,0.2},{2,0.3},{3,0.4},{4,0.5}}
> 
> into this one
> 
> {{1/4, 0.2}, {1/2, 0.3}, {3/4, 0.4}, {1, 0.5}}
> 
> The way i did it is through the chain of commands
> 
> firsttable={{1,0.2},{2,0.3},{3,0.4},{4,0.5}};
> 
> 
> top=Max[Table[firsttable[[i,1]],{i,1,Length[firsttable]}]];
> 
> 
> mytable=Do[newtable=ReplacePart[newtable,newtable[[i,1]]/top,{i,
> 1}],{i,1,Length[firsttable]}]
> 
> There must be a more elegant way to do it, but @&# and commands like 
> those are still hard to handle for me, and I could not work it out
> 
> Thanks in advance,
> 
> Ruth
> 
> 

Hi Ruth,

 what about

data = {{1, 0.2}, {2, 0.3}, {3, 0.4}, {4, 0.5}};

data[[All,1]] /= Max[data[[All,1]]];
data

{{1/4, 0.2}, {1/2, 0.3}, {3/4, 0.4}, {1, 0.5}}

?

Peter


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