Re: put some elements to zero

• To: mathgroup at smc.vnet.net
• Subject: [mg101483] Re: [mg101438] put some elements to zero
• From: Adriano Pascoletti <adriano.pascoletti at dimi.uniud.it>
• Date: Wed, 8 Jul 2009 07:12:32 -0400 (EDT)
• References: <200907071146.HAA27467@smc.vnet.net>

In[4]:= L = {{4, 7}, {2, 5}, {3, 5}, {3, 0}, {10, 2}, {8, 7}, {1, 8}, {2,
3},
{5, 8}, {4, 2}, {2, 6}, {9, 8}, {0, 6}, {8, 5}, {8, 9}, {3, 4},
{2, 8}, {6, 8}, {2, 9}, {2, 10}, {9, 9}, {10, 7}, {6, 4}, {10, 8},
{7, 2}, {5, 0}, {8, 4}, {5, 10}, {2, 5}, {4, 0}, {6, 4}, {0, 5},
{8, 4}, {10, 4}, {6, 2}, {5, 4}, {2, 4}, {3, 3}, {6, 5}, {8, 4},
{1, 3}, {1, 2}, {10, 6}, {10, 6}, {0, 1}, {0, 2}, {0, 5}, {1, 0},
{2, 7}, {3, 6}};
x0 = 5;
L /. {x_ /; x < x0, y_} :> {x, 0}
Out[6]= {{4, 0}, {2, 0}, {3, 0}, {3, 0}, {10, 2}, {8, 7}, {1, 0}, {2, 0},
{5, 8}, {4, 0}, {2, 0}, {9, 8}, {0, 0}, {8, 5}, {8, 9}, {3, 0},
{2, 0}, {6, 8}, {2, 0}, {2, 0}, {9, 9}, {10, 7}, {6, 4}, {10, 8},
{7, 2}, {5, 0}, {8, 4}, {5, 10}, {2, 0}, {4, 0}, {6, 4}, {0, 0},
{8, 4}, {10, 4}, {6, 2}, {5, 4}, {2, 0}, {3, 0}, {6, 5}, {8, 4},
{1, 0}, {1, 0}, {10, 6}, {10, 6}, {0, 0}, {0, 0}, {0, 0}, {1, 0},
{2, 0}, {3, 0}}

2009/7/7 Luigi B <L.Balzano at gmail.com>

> Dear All,
>  I have a matrix with only two columns and many rows. For instance
> {xi,yi}.
> For those xi<x0, I would like to set yi=0.
> I can only think of a very inefficient loop...
>
> thanks
> -Luigi-
>
>

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