Re: i don't understand mapping function over a long list

• To: mathgroup at smc.vnet.net
• Subject: [mg47819] Re: i don't understand mapping function over a long list
• From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
• Date: Thu, 29 Apr 2004 00:33:36 -0400 (EDT)
• Organization: Universitaet Leipzig
• References: <c6l7v9\$iq0\$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```Hi,

a) you can't get {{x\$299, x\$300, x\$301} + 2,..}
because Mathematica will distribute the scalar
addition over the lists an you will always end
with {{x\$299+2, x\$300+2, x\$301+2},..}
b) you can use an new symbol that is not a List with

l = vector @@@ Partition[Flatten[{Table[Unique[x], {n, 1, 30}]}], 3];

and
l+2

c) you can assign the result to

unames = Table[Unique[u], {10}];

with

Set @@@ Transpose[{unames, (l + 2)}]

Regards
Jens

will produce the desired result.

sean kim wrote:
>
> hello group.
>
> i just don't get this.
>
> I'm not sure what's the problem is.
>
> please consider the following list of lists.
>
> l = Partition[Flatten[{Table[Unique[x], {n, 1, 30}]}], 3 ]
>
> above generates a list of 10 lists with 3 elements in each as in...
>
> {
> {x\$299, x\$300, x\$301}, {x\$302, x\$303, x\$304},
> {x\$305, x\$306, x\$307}, {x\$308, x\$309, x\$310},
> {x\$311, x\$312, x\$313}, {x\$314, x\$315, x\$316},
> {x\$317, x\$318, x\$319}, {x\$320, x\$321, x\$322},
> {x\$323, x\$324, x\$325}, {x\$326, x\$327, x\$328}
> }
>
> Now suppose I want to use each of the list( all 10 of them) as a part
> of a function. . I want to "Apply" the function to every list(so, 10
> times in total)
> for a simple examplel let's add 2 to the lists
>
> In[21]:= Apply[Plus@@xlist, 2]
> Out[21]= 2
>
> that didn't work. i wanted to get was
>
> {{x\$299, x\$300, x\$301} + 2,
> {x\$302, x\$303, x\$304} + 2...
> {x\$326, x\$327, x\$328} + 2}}
>
> then i want to give each of the results unique names and use the
> renamed list of lists as an argument in another function.
>
> {
> uniquexname1 = {x\$299, x\$300, x\$301} + 2,
> uniquexname2 = {x\$302, x\$303, x\$304} + 2...
> uniquexname10 = {x\$326, x\$327, x\$328} + 2}
> }
>
> and
>
> Map[Plus, xlist, 2]
>
> just bring back the list itself.
>
> This problem recurs for me. and I think i have problems with it
> because I just don't understand how Mathematica language works.
>
> Reading the book an dhelp manual doesn't help me much in understanding
> what lies underneath.  Can you guys shed soem light on this with some
> simple examples that use numerical operations?
>
> Maybe I'm asking a lot, but any and all insights are thoroughly
> appreciated.
>
>
> sean

```

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