Clear subscripted variables

[Mukhtar Bekkali]

Here is the code (x\_i stands for x subscript i):

Table[{Print[x\_i = i]; Clear[x]; Remove[x]; Unset[x]; Print[x\_i]},
{i, 1, 2}]

I expected that x\_i is cleared at the end of the loop but it isn't

If I insert Clear[Subscript] in the loop then it is cleared, but not
desirable since it clears all variables with subscripts.

What command shall I use to clear specific subscripted variables?

Mukhtar Bekkali

[Pratik Desai]

Mukhtar Bekkali wrote:

Hi,
Here is what I think the problem is
Why is x equal to x\_i?
Even if it is, how can mathematica know it

I think what you can try is
Table[Subscript[x, i] = 1, {i, 1, 2}]
(*Table[Unset[Subscript[x, i]], {i, 1, 2}]
Table[Subscript[x, i], {i, 1, 2}]*)

You can uncomment the unset table to clear the variables, or better yet
write a module to do it (i.e Unset the subscipted variables)

Here is a rough version of the same

unsetmod[x_, list_] := Module[{list1}, list1 =
list; Table[Unset[Subscript[x, list1[[s]]]], {s, 1, Length[list]}]]

Table[Subscript[x, i] = 1, {i, 1, 5}]
(*unsetmod[x, Range[2]]*)
Table[Subscript[x, i], {i, 1, 5}]

Best regards
Pratik

--
Pratik Desai
Graduate Student
UMBC
Department of Mechanical Engineering
Phone: 410 455 8134

[David Bailey]

Hi,

Try this:

Table[a\_i =. , {i, 1, 10}]

This is equivalent to the use of Unset[a\_i]

David Bailey
http://www.dbaileyconsultancy.co.uk

[Jean-Marc Gulliet]

Hi Mukhtar,

Subscripted variables are not symbols in Mathematica: *Clear* and
*Remove* complain about that whereas *Unset* works.

You can use the package *Symbolize* to more or less transform
subscripted variables into symbols. For example,

In[1]:=
\!\(x\_1 = 1\)
Out[1]=
1
In[2]:=
\!\(x\_1\)
Out[2]=
1
In[3]:=
\!\(Clear[x\_1]\)
From In[3]:=
\!\(\*
RowBox[{\(Clear::"ssym"\), \(\(:\)\(\ \)\), "\<\"\\!\\(x\\_1\\) is
not a \
symbol or a string. \\!\\(\\*ButtonBox[\\\"More\[Ellipsis]\\\",
ButtonStyle->\
\\\"RefGuideLinkText\\\", ButtonFrame->None,
ButtonData:>\\\"Clear::ssym\\\"]\
\\)\"\>"}]\)
In[4]:=
\!\(Remove[x\_1]\)
From In[4]:=
\!\(\*
RowBox[{\(Remove::"ssym"\), \(\(:\)\(\ \)\), "\<\"\\!\\(x\\_1\\) is
not a \
symbol. \\!\\(\\*ButtonBox[\\\"More\[Ellipsis]\\\", \
ButtonStyle->\\\"RefGuideLinkText\\\", ButtonFrame->None, \
ButtonData:>\\\"Remove::ssym\\\"]\\)\"\>"}]\)
In[5]:=
\!\(FullForm[HoldForm[x\_1]]\)
Out[5]//FullForm=
HoldForm[Subscript[x,1]]
In[6]:=
\!\(Unset[x\_1]\)
In[7]:=
\!\(x\_1\)
Out[7]=
\!\(x\_1\)
In[8]:=
Needs["Utilities`Notation`"]
In[9]:=
\!\(\*
RowBox[{"Symbolize", "[",
TagBox[\(x\_1\),
NotationBoxTag,
TagStyle->"NotationTemplateStyle"], "]"}]\)
In[10]:=
\!\(x\_1 = 2\)
Out[10]=
2
In[11]:=
\!\(Clear[x\_1]\)
In[12]:=
\!\(x\_1\)
Out[12]=
\!\(x\_1\)

Hope this helps,
/J.M.

[Jens-Peer Kuska]

Hi,

ClearSubscript[x_Symbol] := (First /@
Select[DownValues[Subscript],
MatchQ[First[#],
Verbatim[HoldPattern][Subscript[x, _]]] &]) /.
HoldPattern :> Unset

and

ClearSubscript[x] will remove all Subscript[x,_]
values.

Regards

Jens

"Mukhtar Bekkali" <mbek...@gmail.com> schrieb im
Newsbeitrag news:d9ispk$cpd$1...@smc.vnet.net...