Re: Not-understandable warning

*To*: mathgroup at smc.vnet.net*Subject*: [mg130397] Re: Not-understandable warning*From*: Bob Hanlon <hanlonr357 at gmail.com>*Date*: Mon, 8 Apr 2013 00:06:57 -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*References*: <20130407015306.AC8EC6AC8@smc.vnet.net>

$Version 9.0 for Mac OS X x86 (64-bit) (January 24, 2013) mat = SparseArray[ {{i_, i_} -> 1}, {4, 4}] SparseArray[<4>, {4, 4}] mat2 = SparseArray[ Table[{i, i} -> 1, {i, 4}]] SparseArray[<4>, {4, 4}] mat3 = IdentityMatrix[4]// SparseArray SparseArray[<4>, {4, 4}] mat == mat2 == mat3 == IdentityMatrix[4] True Bob Hanlon On Sat, Apr 6, 2013 at 9:53 PM, <JikaiRF at aol.com> wrote: > Dear members: > > I have a difficulty to understand programming in Mathematica. > > I input the following, based on a textbook titled ``Programming with > Mathematica: An Introduction" by Paul Wellin, which is published by > Cambridge University Press. > > mat = SparseArray[{i_, i_} \[RightArrow] 1, {4, 4}] > > Then, I received an answer as > > SparseArray[{i_, i_} \[RightArrow] 1, {4, 4}] > > with a warning as > > `` SparseArray::list: "List expected at position 1 in SparseArray[{i_, > i_} \[RightArrow] 1, {4, 4}]". > > In this textbook, on page 32, there appears a correct answer as follows: > > SparseArray[<4>, {4,4}]. > > Why my Mathematica cannot understand my input? > > By the way, I use Mathematica 8.0.4.0 version and Mac OS 10.5.8. > > Sincerely, > Fujio Takata. > > > > > > >

**References**:**Not-understandable warning***From:*JikaiRF@aol.com