Re: Manipulate a Plot of Evaluate DSolve

*To*: mathgroup at smc.vnet.net*Subject*: [mg127504] Re: Manipulate a Plot of Evaluate DSolve*From*: Alexei Boulbitch <Alexei.Boulbitch at iee.lu>*Date*: Mon, 30 Jul 2012 22:12:56 -0400 (EDT)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*Delivered-to*: l-mathgroup@wolfram.com*Delivered-to*: mathgroup-newout@smc.vnet.net*Delivered-to*: mathgroup-newsend@smc.vnet.net

Hi, I'm trying to Manipulate a Plot of a quite difficult function which involves solving a differential equation, but cannot be solved analytically. To try to simplify the example and simulate it, let's assume that we have the following function: func[coef_] = {{y -> Function[{x}, DSolve[y'[x] == Cos[coef *x], y, x]]}} Manipulate[Plot[{{Evaluate[y[x] /. func[coef] /. C[1] -> {Range[-5, 0]}]}},{x, -10, 10}], {{coef , 1}, 0.1, 5}] I get an error: DSolve::dsvar: "-9.99959 cannot be used as a variable" I think that this is because Manipulate assigns a value to x (= -9.99959)BEFORE solving the DSolve, even though to avoid it I'm using the Evaluate function, which should process the function before assigning a value to x. But the thing is that the "coef" to be Manipulated is at the same "level" as the x in the Manipulate block, so probably if I need the coef to solve the DSolve, I also have the x that gives me an error. Is there any workaround? I guess I'm not understanding properly how Mathematica processes these simple expressions. Thanks, Juan Hi, Juan, Try this: Manipulate[ Plot[Evaluate[ y[x] /. DSolve[{y'[x] == Cos[coef*x]}, y, x] /. C[1] -> Range[-5, 0]], {x, -10, 10}], {{coef, 1}, 0.1, 5}] Have fun, Alexei Alexei BOULBITCH, Dr., habil. IEE S.A. ZAE Weiergewan, 11, rue Edmond Reuter, L-5326 Contern, LUXEMBOURG Office phone : +352-2454-2566 Office fax: +352-2454-3566 mobile phone: +49 151 52 40 66 44 e-mail: alexei.boulbitch at iee.lu