MathGroup Archive 2007

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: Sort problem

  • To: mathgroup at
  • Subject: [mg81732] Re: Sort problem
  • From: Bill Rowe <readnewsciv at>
  • Date: Tue, 2 Oct 2007 05:43:23 -0400 (EDT)

On 10/1/07 at 4:49 AM, donabc at (Donald DuBois) wrote:

>This Sort works

>In[32]:= Sort[{r, a, x}]

>Out[32]= {a, r, x}

>but this one doesn't:

>In[33]:= Sort[{{r, 2}, {a, 3}, {x, 4}}, #1[[1]] < #2[[1]] &]

>Out[33]= {{r, 2}, {a, 3}, {x, 4}}

>What am I doing wrong?

In the first example above, no specific sort function is
specified, so Mathematica puts the items in canonical order. In
the second example, you have specified a pure function as the
test function and given none of the symbols have assigned values
the function returns neither true nor false. Consequently, the
order is unchanged.

You can achieve what you want with:

In[3]:= data = {{r, 2}, {a, 3}, {x, 4}};
data[[Ordering[First /@ data]]]

Out[4]= {{a, 3}, {r, 2}, {x, 4}}
To reply via email subtract one hundred and four

  • Prev by Date: Re: Sort problem
  • Next by Date: Re: Other bug in ContourPlot
  • Previous by thread: Re: Sort problem
  • Next by thread: Re: Sort problem