Hex, Bugs and More Physics | Emre S. Tasci

Mathematica Matrix Manipulation Examples

B={Range[5],Range[6,10],Range[11,15],Range[16,20]} ;
TableForm[B]

(* To extract rows 2 & 3 *)
Part[B,{2,3}] // TableForm

(* To extract cols 2 & 4 *)
Part[B, All,{2,4}] // TableForm

(* To extract the intersection of Rows 2&3 with Cols 2&4 *)
Part[B,{2,3} ,{2,4}] // TableForm

(* Selecting the values from the 2. row where B[[4]][[i]] has a specific value like <10 *)
Select[B[[2]],#<10&]

(* Selecting the values from the 2. col where B[[i]][[2]] has a specific value like <10 *)Select[Part[B,All,2],#<10&]

(* Alternative Transpose (//Equivalent to Transpose[matrixIN]//)*)
TransposeEST[matrixIN_]:=Module[
{matrixOUT},
numCols = Dimensions[matrixIN][[2]];
matrixOUT = Array[mo,numCols];
For[i=1,i<=numCols,i++,
� � � matrixOUT[[i]]=Part[matrixIN,All,i];
]
TableForm[matrixOUT];
Return[matrixOUT];
]

(* Swapping two rows *)
({B[[2]],B[[4]]}={B[[4]],B[[2]]}) // TableForm

(*Reading data from a file with a content like this:
 0.642864000  0.761961000  1.665420000 
 5.815150000  3.603020000  1.831920000 
 6.409050000  7.150810000  0.966674000 
 5.389080000  4.989350000  6.571080000 
 6.044070000  4.887170000  7.005700000 
 6.806280000  2.766540000  4.030720000 
 6.676540000  0.652834000  5.729050000 
 1.231490000  5.754580000  0.404114000 
 9.722660000  7.571420000  1.133980000 
 8.869320000  7.574570000  4.886290000 
 1.221750000  8.511380000  6.201370000 
 2.817450000  0.216682000  6.474590000 
 5.638430000  7.422500000  7.381840000 
 8.903770000  4.192770000  0.355182000 
 7.073810000  1.421990000  1.606240000 
 7.646660000  1.979770000  3.877830000 
 8.239190000  1.280060000  6.705840000 
 4.430740000  2.016050000  5.515660000 
 9.771000000  2.637290000  8.423900000 
 8.916410000  4.900040000  2.592560000
*)

m=OpenRead["d:\lol1.txt"];
k= ReadList[m,Number];
Close[m];
(k =Partition[k,3]) // TableForm

(* And you can definitely Plot it too *)
<<Graphics`Graphics3D`
ScatterPlot3D[k,PlotStyle®{{PointSize[0.04],GrayLevel[0.09]}}]