A Dynamic mess

*To*: mathgroup at smc.vnet.net*Subject*: [mg92925] A Dynamic mess*From*: chandler.seth at gmail.com*Date*: Mon, 20 Oct 2008 07:32:31 -0400 (EDT)

There has just got to be an easier way to do the following. The example is somewhat silly, but if I could understand how to do this competently, I would learn a lot. Suppose I want to compute the sum of an integer (z) and a value chosen from some uniform distribution on the interval 0 to a. I want to do this interactively and I do NOT want the draw from the random distribution to change when I change z, just when I change the parameter a. So, we create the number z as follows: z=6;SetterBar[Dynamic[z],{6,7,8}] If I do the following, it does not work as expected because, I suppose, Dynamic[z] is a FrontEnd object in its heart of hearts (a DynamicBox) and thus does not add to 2 the way an integer would. Dynamic[z]+2 So, this can be fixed with Dynamic[z+2] OK, now instead of adding 2, let's add some random value a=0.5;Slider[Dynamic[a]]; Dynamic[z+RandomReal[{0,Setting@Dynamic[a]}]] (* setting is added because if one just uses Dynamic[a] one is referencing a front end object rather than an actual number*) This evaluates, but it does not have the desired behavior. Now, when I change z I also get a new draw from the random distribution. I thought of trying to blocking the redraw by wrapping Dynamic around the RandomReal, like this. Dynamic[z+Dynamic@RandomReal[{0,Setting@Dynamic[a]}]] But that doesn't work at all. It still redraws when I change z and the addition no longer works in the desired way since the Dynamic expression is not "really" a number but just a box. I can solve the latter problem by wrapping a Setting in front of the Dynamic Dynamic[z + Setting@Dynamic[RandomReal[{0, Setting@Dynamic[a]}]]] Now it adds properly but it still refreshes the random draw every time I change z. This doesn't work either and the expression is getting awfully complicated Dynamic[z + Refresh[Setting@Dynamic[RandomReal[{0, Setting@Dynamic[a]}]], TrackedSymbols -> {a}]] And this doesn't work either Dynamic[Setting@Dynamic[z] + Setting@Dynamic[RandomReal[{0, Setting@Dynamic[a]}]]] Can someone help!