       Re: Could we build matrix with codition instruction?

• To: mathgroup at smc.vnet.net
• Subject: [mg23347] Re: [mg23314] Could we build matrix with codition instruction?
• From: Matt.Johnson at autolivasp.com
• Date: Thu, 4 May 2000 02:59:15 -0400 (EDT)
• Sender: owner-wri-mathgroup at wolfram.com

```
This may not be the most eloquent way, but

In:=
mat = Array[f, {4, 4}]

Out=
{{f[1, 1], f[1, 2], f[1, 3], f[1, 4]}, {f[2, 1], f[2, 2], f[2, 3],
f[2, 4]}, {f[3, 1], f[3, 2], f[3, 3], f[3, 4]}, {f[4, 1], f[4, 2],
f[4, 3], f[4, 4]}}

In:=
g[i_, j_] := If[(j - i) >= 0, mat[[i, j]] = 1, mat[[i, j]] = 0]

In:=
Table[g[i, j], {i, 4}, {j, 4}]

Out=
{{1, 1, 1, 1}, {0, 1, 1, 1}, {0, 0, 1, 1}, {0, 0, 0, 1}}

In:=
mat

Out=
{{1, 1, 1, 1}, {0, 1, 1, 1}, {0, 0, 1, 1}, {0, 0, 0, 1}}

-matt

Coase Yang <cnc at ms6.hinet.net> on 05/01/2000 04:00:15 PM

Subject: [mg23347]  [mg23314] Could we build matrix with codition instruction?

Dear All:

I want to construct an 4*4 upper triangular matrix with
conditional instruction, a[i,j]:
if j-i>=0, then a[[i,j]]=1
if j-i<0, then a[[i,j]]=0
Could anyone tell me how I could build this matrix with
list or Table form by conditional instruction inside?

Thank you very much.

Coase Yang

```

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