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Re: Create and use a set of values for variables

  • To: mathgroup at
  • Subject: [mg107532] Re: [mg107519] Create and use a set of values for variables
  • From: "David Park" <djmpark at>
  • Date: Tue, 16 Feb 2010 03:52:27 -0500 (EST)
  • References: <9300874.1266231914378.JavaMail.root@n11>

I'm not certain if I understand your question but you could use SubValues to
enter the parameters d,e,f and calculate a,b,c.

y[d_, e_, f_][x_] :=
 With[{a = d^2, b = d + e, c = 2 f},
  a x^2 + b x + c]  


y[d, e, f][x] 
2 f + (d + e) x + d^2 x^2  

With numbers:

y[5, 5, 1][x] 
2 + 10 x + 25 x^2  

You can even easily compute the derivative (in case you want that).

y[5, 5, 1]'[x]  
10 + 50 x 

And plot both of them:

Plot[{y[5, 5, 1][x], y[5, 5, 1]'[x]}, {x, -5, 5}]   

David Park
djmpark at  

From: Menl [mailto:szegersnl at] 


I try to find a method of doing the following in Mathematica. 

I have some function y[x_]=a x^2 + b x + c 
Now I want some list which hold values for a, b and c. that are dependend on
some lower level values d, e and f. 

vars1=[{d=1, e=4, f=6},{b=d+e, c=2f, a = d^2}] 
vars2=[{d=2, e=3, f=7},{b=d+e, c=2f, a = d^2}] 
vars3=[{d=5, e=5, f=1},{b=d+e, c=2f, a = d^2}] 

and use these sets with the original function when I need it. 

This line will not work as intended of course but I hope it makes it clear
what I try to do. The key is I would like to not evaluate these values
outside this vars, so the original function stays unevaluated. 

Something like this I tried to do with either the functions Block or With,
but both evaluate the values for a, b and c. I would like to make several
such sets of variables without evaluating them so I can use them as desired,
to plot the original function with several sets of vars.

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