Manipulate variables not getting evaluated

*To*: mathgroup at smc.vnet.net*Subject*: [mg122824] Manipulate variables not getting evaluated*From*: Ken Levasseur <klevasseur at mac.com>*Date*: Fri, 11 Nov 2011 04:57:03 -0500 (EST)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com

Hello I'm trying to control, using Manipulate, which rows of a matrix are displayed. But have run into a problem. The code I annotate here is copied without comments below. For this example, I'll use this 2 by 3 matrix A = {{1, 2, 3}, {4, 5, 6}}; The following works pretty much as I intend, although there is fixable problem if all boxes are unchecked. Manipulate[ Transpose[Transpose[A][[Select[Range[3], {a, b, c}[[#1]] & ]]]], Evaluate[Sequence @@ {{a, {True, False}}, {b, {True, False}}, {c, {True, False}}}]] Now I want to do the same for larger matrices with various numbers of columns so I've tried generalizing as follows: Number of columns: M = 3; This generates a list of M symbols: col1, col2,=85 switchlist = (ToExpression[StringJoin["col", ToString[#1]]] & ) /@ Range[M]; This generates a list of controllers for each symbol=85 switches = ({ToExpression[StringJoin["col", ToString[#1]]], {True, False}} & ) /@ Range[M]; Now I expected this to work, but it fails: Manipulate[ Transpose[Transpose[A][[Select[Range[M], switchlist[[#1]] & ]]]], Evaluate[Sequence @@ switches]] The problem is that the symbols in switchlist don't get evaluated. Manipulate[switchlist, Evaluate[Sequence @@ switches]] I've tried using controllers like {{col1,True},{True,False}} and that doesn't make a difference. Any idea why this fails? Ken Levasseur UMass Lowell ****************** Code only: A = {{1, 2, 3}, {4, 5, 6}}; Manipulate[ Transpose[Transpose[A][[Select[Range[3], {a, b, c}[[#1]] & ]]]], Evaluate[Sequence @@ {{a, {True, False}}, {b, {True, False}}, {c, {True, False}}}]] M = 3; switchlist = (ToExpression[StringJoin["col", ToString[#1]]] & ) /@ Range[M]; switches = ({ToExpression[StringJoin["col", ToString[#1]]], {True, False}} & ) /@ Range[M]; Manipulate[ Transpose[Transpose[A][[Select[Range[M], switchlist[[#1]] & ]]]], Evaluate[Sequence @@ switches]] Manipulate[switchlist, Evaluate[Sequence @@ switches]]