Re: Giving an arbitrary number of arguments to Manipulate using Apply
- To: mathgroup at smc.vnet.net
- Subject: [mg94674] Re: [mg94635] Giving an arbitrary number of arguments to Manipulate using Apply
- From: "David Park" <djmpark at comcast.net>
- Date: Fri, 19 Dec 2008 07:26:41 -0500 (EST)
- References: <20783330.1229605981096.JavaMail.root@m02>
Sometimes I put Print statements into the code so I can see what the
intermediate expressions are. The problem here is to prevent the Plot from
being evaluate until after it is in the Manipulate statement. So use a dummy
plot function and then substitute Plot after the Manipulate statement is
composed. (Manipulate has the Attribute HoldAll.)
testFunc[expr_, vars_] :=
Module[{newFunc, args, i, p, plotf},
newFunc = Apply[Plus, expr] /. vars[[1]] -> p;
Print[newFunc];
args :=
Join[{plotf[newFunc, {p, 0, 10},
Epilog -> Text[vars[[1]], Scaled[{.5, .9}]]]},
Table[{vars[[i]], 0, 10}, {i, 1, Length[vars]}]];
Print[args];
Apply[Manipulate, args] /. plotf -> Plot]
testFunc[{Sin[a x], b + x^2, -b x}, {x, a, b}]
David Park
djmpark at comcast.net
http://home.comcast.net/~djmpark/
From: Yoichi Aso [mailto:aso at caltech.edu]
Hello,
I have a problem with using Manipulate and Apply.
I'd like to ask for your advice on this.
Here is what I want to do:
I have a list of expressions, expr, and a list of variables, vars.
Each element of expr is a function of variables in vars.
For example, expr={Sin[a x], x^2+b, - b x}; vars = {x,a,b}.
Now, I want to write a function which takes expr and vars as arguments
and does the following.
First, it adds together the elements of expr to make a new function,
newFunc.
Then it creates a Manipulate object with sliders for all the variables in
vars.
The first argument of the Manipulate is a Plot of newFunc as a
function of the first variable
in vars.The value of the other variables are determined by the
sliders. Along with the plot,
the value of the first variable is shown as a Text object in the plot.
Here is a code I came up with to implement the above task.
testFunc[expr_, vars_] := Module[{newFunc, args, i, p},
newFunc = Apply[Plus, expr] /. vars[[1]] -> p;
args :=
Join[{Plot[newFunc, {p, 0, 10}, Epilog -> Text[vars[[1]], {5, 1}]]},
Table[{vars[[i]], 0, 10}, {i, 1, Length[vars]}]];
Apply[Manipulate, args]
]
However, when I execute, for example,
testFunc[{Sin[a x], b + x^2, -b x}, {x, a, b}]
it shows nothing in the plot area.
I'm guessing it is because Join tries to evaluate the arguments, and
at this moment, Plot cannot draw a graph
because the variables a and b do not have numerical values.
I enclosed the Join with Hold and used ReleaseHold around the Apply,
but still no plot shown.
I used Apply because I don't know the length of vars in advance.
I'd appreciate it if anyone can suggest a solution to this problem.
Thank you in advance,
Yoichi
--
----------------------------------------
Yoichi Aso
LIGO Laboratory, California Institute of Technology
aso at caltech.edu or asoy01 at gmail.com