Re: How to reverse sign on the y's in a list of (x, y)'s?
- To: mathgroup at smc.vnet.net
- Subject: [mg61267] Re: [mg61231] How to reverse sign on the y's in a list of (x, y)'s?
- From: János <janos.lobb at yale.edu>
- Date: Fri, 14 Oct 2005 05:54:09 -0400 (EDT)
- References: <200510130539.BAA04564@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
On Oct 13, 2005, at 1:39 AM, sherifffruitfly at gmail.com wrote:
> Hi all,
>
> This is really dumb, but I just don't know how to do it...
>
> Import from excel gives me a list of ordered pairs, and I want the 2nd
> element of each pair to be of opposite sign. Sticking the negative
> sign
> in front of the entire Import statement reverses both the 1st and the
> 2nd elements (duh). How do I get just the second item to reverse sign?
>
> thanks!
Here is a newbie approach:
In[1]:=
lst = Table[{x, (-1)^i*y},
{i, 1, 5}]
Out[1]=
{{x, -y}, {x, y}, {x, -y},
{x, y}, {x, -y}}
In[2]:=
newlst =
({#1[[1]], -#1[[2]]} & ) /@
lst
Out[2]=
{{x, y}, {x, -y}, {x, y},
{x, -y}, {x, y}}
János
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Trying to argue with a politician is like lifting up the head of a
corpse.
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- References:
- How to reverse sign on the y's in a list of (x, y)'s?
- From: sherifffruitfly@gmail.com
- How to reverse sign on the y's in a list of (x, y)'s?