Re: Problem in Evaluate/Manipulate

*To*: mathgroup at smc.vnet.net*Subject*: [mg88657] Re: Problem in Evaluate/Manipulate*From*: Szabolcs Horvát <szhorvat at gmail.com>*Date*: Sun, 11 May 2008 15:16:25 -0400 (EDT)*Organization*: University of Bergen*References*: <g03v2l$bno$1@smc.vnet.net>

wiso wrote: > I have a problem with this code: > > Solution =DSolve[{x^\[Prime][t]==a x[t]+b y[t],y^\[Prime][t]==c x[t]+d > y[t],x[0]==x0,y[0]==-10},{x[t],y[t]},t]; > > Manipulate[ > Solutions = Evaluate [Table[{x[t],y[t]}/.Solution[[1]], > {x0,-10,10,10}]] > ,{a,-1,1},{b,-1,1},{c,-1,1},{d,-1,1}] > > I want to solve only one time the PDE, then I placed it outside the > Manipulate. The code doesn't evaluate the solution with the dynamic > values. > Remove "Solutions =". From the doc page of Evaluate: "Evaluate only overrides HoldFirst, etc. attributes when it appears directly as the head of the function argument that would otherwise be held." This will work: Manipulate[ Evaluate[Solutions = Table[{x[t], y[t]} /. Solution[[1]], {x0, -10, 10, 10}]], {a, -1, 1}, {b, -1, 1}, {c, -1, 1}, {d, -1, 1}]