use At() instead of indexer if possible

src/Numerics/LinearAlgebra/Generic/Matrix.cs

@@ -110,7 +110,7 @@ namespace MathNet.Numerics.LinearAlgebra.Generic
             {
                 for (var i = 0; i < columnVectors[j].Count; i++)
                 {
-                    matrix.At(i, j, columnVectors[j][i]);
+                    matrix.At(i, j, columnVectors[j].At(i));
                 }
             }
 
@@ -149,7 +149,7 @@ namespace MathNet.Numerics.LinearAlgebra.Generic
             {
                 for (var j = 0; j < rowVectors[i].Count; j++)
                 {
-                    matrix.At(i, j, rowVectors[i][j]);
+                    matrix.At(i, j, rowVectors[i].At(j));
                 }
             }
 
@@ -640,7 +640,7 @@ namespace MathNet.Numerics.LinearAlgebra.Generic
 
             for (var i = 0; i < min; i++)
             {
-                diagonal[i] = At(i, i);
+                diagonal.At(i, At(i, i));
             }
 
             return diagonal;
@@ -962,7 +962,7 @@ namespace MathNet.Numerics.LinearAlgebra.Generic
 
             for (var i = 0; i < min; i++)
             {
-                At(i, i, source[i]);
+                At(i, i, source.At(i));
             }
         }
 

src/Numerics/LinearAlgebra/Generic/Vector.BCL.cs

@@ -96,7 +96,7 @@ namespace MathNet.Numerics.LinearAlgebra.Generic
         {
             for (int i = 0; i < Count; ++i)
             {
-                if (this[i].Equals(item))
+                if (At(i).Equals(item))
                     return i;
             }
             return -1;

src/Numerics/LinearAlgebra/Generic/Vector.cs

@@ -881,7 +881,7 @@ namespace MathNet.Numerics.LinearAlgebra.Generic
 
             for (var i = 0; i < u.Count; i++)
             {
-                matrix.SetRow(i, v.Multiply(u[i]));
+                matrix.SetRow(i, v.Multiply(u.At(i)));
             }
 
             return matrix;
@@ -1210,7 +1210,7 @@ namespace MathNet.Numerics.LinearAlgebra.Generic
         /// <returns>The value of maximum element.</returns>
         public T Maximum()
         {
-            return this[MaximumIndex()];
+            return At(MaximumIndex());
         }
 
         /// <summary>
@@ -1225,7 +1225,7 @@ namespace MathNet.Numerics.LinearAlgebra.Generic
         /// <returns>The value of the minimum element.</returns>
         public T Minimum()
         {
-            return this[MinimumIndex()];
+            return At(MinimumIndex());
         }
 
         /// <summary>