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Re: Creating a list of 1x2 element arrays without

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  • Subject: [mg132081] Re: Creating a list of 1x2 element arrays without
  • From: Itai Seggev <itais at wolfram.com>
  • Date: Mon, 2 Dec 2013 01:57:42 -0500 (EST)
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On Sun, Dec 01, 2013 at 08:23:45AM -0500, amannucci wrote:
> Is there a way in Mathematica using built-in functions to create what the following procedural program does?
> 
> latlong = {}
> Do[AppendTo[latlong, {i, j}] , {i, 30.0, 45.0, 
>    5.0}, {j, -270.0, -240.0, 10.0}];
> latlong
> 
> Out:
> {{30., -270.}, {30., -260.}, {30., -250.}, {30., -240.}, {35., \
> -270.}, {35., -260.}, {35., -250.}, {35., -240.}, {40., -270.}, {40., \
> -260.}, {40., -250.}, {40., -240.}, {45., -270.}, {45., -260.}, {45., \
> -250.}, {45., -240.}}
> 
> Thanks!
> 
> -Tony

You can easily fix up the list structure with Flatten.  Note that this is much
more efficient for large datasets than your procedural code, which has
complexity O(n^2) with n the total number of pairs. 

In[63]:= Flatten[
 Table[{i, j}, {i, 30.0, 45.0, 5.0}, {j, -270.0, -240.0, 10.0}], 1]

Out[63]= {{30., -270.}, {30., -260.}, {30., -250.}, {30., -240.}, \
{35., -270.}, {35., -260.}, {35., -250.}, {35., -240.}, {40., -270.}, \
{40., -260.}, {40., -250.}, {40., -240.}, {45., -270.}, {45., -260.}, \
{45., -250.}, {45., -240.}}
 
--
Itai Seggev
Mathematica Algorithms R&D
217-398-0700 



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