Drexel dragonThe Math ForumDonate to the Math Forum



Search All of the Math Forum:

Views expressed in these public forums are not endorsed by Drexel University or The Math Forum.


Math Forum » Discussions » Software » comp.soft-sys.math.mathematica

Topic: Map
Replies: 2   Last Post: May 25, 2013 5:34 AM

Advanced Search

Back to Topic List Back to Topic List Jump to Tree View Jump to Tree View   Messages: [ Previous | Next ]
Bob Hanlon

Posts: 906
Registered: 10/29/11
Re: Map
Posted: May 25, 2013 5:33 AM
  Click to see the message monospaced in plain text Plain Text   Click to reply to this topic Reply

hklist = Array[h, {5, 3}];


bragg = {b1, b2, b3};


qbarlist = Map[(# - bragg) &, hklist, {2, 2}];


As stated in the documentation (
http://reference.wolfram.com/mathematica/ref/Map.html ), the third argument
to Map is the level specification and the form {n1, n2} specifies levels n1
through n2. In this case n1 and n2 are equal so it is equivalent to just
{n1}.


qbarlist === Map[(# - bragg) &, hklist, {2}]


True


If you look at your outputs carefully you will see that you do not get the
same result with a third argument of {1}


qbarlist === Map[(# - bragg) &, hklist, {1}]


False


qbarlist // Dimensions


{5, 3, 3}


Map[(# - bragg) &, hklist, {1}] // Dimensions


{5, 3}


Examine the two different arrays above to understand the different behavior.



Bob Hanlon


On Fri, May 24, 2013 at 6:25 AM, Jon Morris <djpmorris@googlemail.com>wrote:

> I'm new to Mathematica and I've been given some code to help me analyse
> some data. I'm trying to understand what the Map function does,
> specifically what the {2,2} means?
>
> qbarlist = Map[(# - bragg) &, hkllist,{2, 2}];
>
> hklist is a 3 column list, bragg is a three element vector.
>
> When I try the same line with {2} or {1} I seem to get the same answer.
> The online explanation of this term does not make that much sense to me.
> I'd be very grateful if someone could explain the purpose of the last term
> of the Map syntax.
>
> Thanks,
> Jon
>
>





Date Subject Author
5/25/13
Read Re: Map
Bob Hanlon
5/25/13
Read Re: Map
Jon Morris

Point your RSS reader here for a feed of the latest messages in this topic.

[Privacy Policy] [Terms of Use]

© Drexel University 1994-2014. All Rights Reserved.
The Math Forum is a research and educational enterprise of the Drexel University School of Education.