<apmatrix.h>
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apmatrix variables are declared
in a similar manner to
apvector variables, but they work with two arguments:
the number of rows, followed by the number of columns. |
//declare a matrix of doubles with 5 rows and 3 columns
apmatrix <double> table(5 , 3);
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You can add a third
argument when declaring matrices.
This "fill" value
must be
of the same "type" as the matrix variables. |
//declare and fill matrix with astericks
apmatrix <char> stars(2, 80, '*');
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Instead of the length( ) function we saw in the
apvector
class, the apmatrix class provides
two functions for accessing the dimensions
of a matrix: numrows( )
and
numcols( ). These member functions of the
apmatrix class are called using "dot" notation.
(Notice the use of the nested loops.) |
//function to return the sum of the
elements in the matrix "table"
int AddElements(const apmatrix<int> &table)
{
int nRows = table.numrows( );
int nCols = table.numcols( );
int row, col, sum = 0;
for(row = 0; row < nRows; row++)
{
for(col = 0; col < nCols; col++)
{
sum += table[row][col];
}
}
return sum;
}
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As with one-dimensional arrays, matrices can be
filled one element at a time after declaration, by assignment or by user input. Here is an example with user input. (Notice the nested loops.) |
apmatrix<int> ClubScores(4 , 5);
// declaring the 2-D array
int rows, columns;
for (rows = 0; rows < 4; rows++)
// loop for establishing the rows
{
for (columns =0; columns < 5; columns++)
// loop for the columns
{
cout << "Please enter a
score ===> ";
cin >>
ClubScores[rows] [columns];
}
}
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Printing Multi-dimensional Arrays
Nested loops are also used to print a matrix: |
apmatrix<int> ClubScores(4 , 5);
int rows, columns;
for (rows = 0; rows < 4; rows++)
{
for (columns =0; columns < 5; columns++)
{
cout << ClubScores[rows] [columns] << " "; //
put in spaces between..
}
// columns when printing
cout << endl;
// a new line is needed to go to the next row
}
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