MinFUNC

[sahebe...@gmail.com]

Hi
how i can get the minimum value of a matrix rows ???
the matrix has n rows and n column.
for example: min (M[1,1]):=10 = M[1,3]   How i can get this???
M[i,j]:=
                 1               2             3    

    
1               20            30           10

 
2               30             40           20
 

3               10             50           60

WBR

[Victor Zverovich]

You can get the minimum with the following expression:

  min{i in 1..3, j in 1..3} M[i, j]

HTH,

Victor

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[sahebe...@gmail.com]

hi
i get minimum value of each rows
please answer me thanks a lot

[Robert Fourer]

The minimum of row i is

min {j in 1..3} M[i,j]

You can use this expression anywhere that the index i is defined. So for example you can specify

param M {1..3,1..3};
param Mmin {i in 1..3} = min {j in 1..3} M[i,j];

Bob Fourer
am...@googlegroups.com

///////

[sahebe...@gmail.com]

hi
thanks Bob for your answer
bat i get Mmin[i,j]
for example the minimum value of first row is on the third column so Mmin:=[1,3]
WBR

[Robert Fourer]

Are you looking for the "arg min" -- the column in which the minimum appears, rather than the value of the minimum? AMPL does not have this kind of min function, but you could write

param M {1..3,1..3};
param Mmin {i in 1..3} = min {j in 1..3} M[i,j];

param MminCol {i in 1..3} = min {j in 1..3: M[i,j] = Mmin[i]} j;

If the minimum occurs in more than one column, the first one will be chosen. This is not especially efficient, but it will be very fast unless your matrix is very large.

Bob Fourer
am...@googlegroups.com

=======

[sahebe...@gmail.com]

thanks a lot