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