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: Adding value to some elements of a list
Replies: 3   Last Post: Jun 6, 2013 7:50 AM

Advanced Search

Back to Topic List Back to Topic List Jump to Tree View Jump to Tree View   Messages: [ Previous | Next ]
David Bailey

Posts: 714
Registered: 11/7/08
Re: Adding value to some elements of a list
Posted: Jun 6, 2013 7:23 AM
  Click to see the message monospaced in plain text Plain Text   Click to reply to this topic Reply

On 05/06/2013 08:15, Joerg Lenhardt wrote:
> Hello,
>
> I have two lists. One containing values, another containing indexes to
> the first list. I want to add a value to all elements of the first list
> when its index is in the second list:
>
> a={10,20,30,40,50,60}
>
> b={2,4,6}
>
> c=17
>
> ==>
>
> {10,20+17,30,40+17,50,60+17}
>
> I would be glad if anyone have a simple solution for that problem - I am
> convinced there is one ...
>
> Best regards
> J. Lenhardt
>

In[1]:= a = {10, 20, 30, 40, 50, 60};

b = {2, 4, 6};

c = 17;


In[4]:= ans = a;

In[5]:= ans[[b]] = ans[[b]] + c;

In[6]:= ans

Out[6]= {10, 37, 30, 57, 50, 77}

To understand this better, remember that [[.....]] is a shorthand for
Part - so look that function up.

David Bailey
http://www.dbaileyconsultancy.co.uk





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.