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Re: Apply function to parts of a list


data = {{x1, y1}, {x2, y2}, {x3, y3}};

{2, 1} # & /@ data

{{2*x1, y1}, {2*x2, y2}, {2*x3, y3}}

data /. {x_, y_} -> {2 x, y}

{{2*x1, y1}, {2*x2, y2}, {2*x3, y3}}


Bob Hanlon

---- guerom00 <guerom00 at gmail.com> wrote: 
> Hi all,
> 
> Very often, I find myself having datas to plot of this form :
> 
> data={{x1,y1},{x2,y2},{x3,y3}...{xn,yn}}
> 
> So, very conventional : a list of abscissa and ordinate. Now, let's say I want to multiply by 2 all my ascissa. Right now, I write :
> 
> MapAt[2*#&,data,Table[{i,1},{i,1,Length[data]}]]
> 
> It's OK but I isn't there another way to achieve this as I find this rather "involved" for such a simple thing ?
> 
> Thanks in advance.
> 



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