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Re: display of function
*To*: mathgroup at smc.vnet.net
*Subject*: [mg58516] Re: display of function
*From*: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>
*Date*: Tue, 5 Jul 2005 04:52:24 -0400 (EDT)
*Organization*: The Open University, Milton Keynes, England
*References*: <dad7oo$t91$1@smc.vnet.net>
*Sender*: owner-wri-mathgroup at wolfram.com
Bosch, Darrell wrote:
> Dear Math Group:
>
> The first equation below shows a function for u(y) which is
> the sum of the products of pi times yi. In the following steps, I
> assign values of p and y. How can I get Mathematica to display the
> numerical value of u for the given p and y values? When I insert the
> u[y] command, I just get a repeat of the equation I have entered.
> Thanks for your suggestions. This group is a great help. Darrell
>
>
>
> u[y_] := Sum[Subscript[p, i]*Subscript[y, i],
>
> {i, 1, n}]
>
>
>
> p = {.3,.4,.3}
>
>
>
> y={10000, 20000, 30000}
>
>
Hi Darrell,
Assuming that I have correctly understood what you tried to do, you
could use either one of the following approaches:
In[1]:=
p = {0.3, 0.4, 0.3}
y = {10000, 20000, 30000}
Out[1]=
{0.3, 0.4, 0.3}
Out[2]=
{10000, 20000, 30000}
We take the product of the corresponding elements in each list
In[3]:=
p*y
Out[3]=
{3000., 8000., 9000.}
Finally, we take the sum of these products
In[4]:=
Plus @@ %
Out[4]=
20000.
This series of operations is indeed the dot product of p and y
In[5]:=
p . y
Out[5]=
20000.
If you need to use some other functions in place of *Plus* and *Times*,
have a look at the *Inner* product.
Best regards,
/J.M.
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