org.lsmp.djep.vectorJep.function.Determinant Maven / Gradle / Ivy
Go to download
Show more of this group Show more artifacts with this name
Show all versions of jep Show documentation
Show all versions of jep Show documentation
JEP is a Java library for parsing and evaluating mathematical expressions. Use groupId org.fudaa to deploy it in maven central
The newest version!
/* @author rich
* Created on 13-Feb-2005
*
* See LICENSE.txt for license information.
*/
package org.lsmp.djep.vectorJep.function;
import java.util.Stack;
import org.lsmp.djep.vectorJep.Dimensions;
import org.lsmp.djep.vectorJep.values.*;
import org.nfunk.jep.ParseException;
import org.nfunk.jep.function.*;
/**
* Calculate the Determinant of a matrix
* det([[1,2],[3,4]]) -> 1*4-2*3 = -2
*
* @author Rich Morris
* Created on 13-Feb-2005
*/
public class Determinant extends PostfixMathCommand implements UnaryOperatorI
{
Add add = new Add();
Subtract sub = new Subtract();
Multiply mul = new Multiply();
public Determinant()
{
super();
this.numberOfParameters = 1;
}
public Dimensions calcDim(Dimensions ldim)
{
return Dimensions.ONE;
}
public MatrixValueI calcValue(MatrixValueI res, MatrixValueI lhs)
throws ParseException
{
if(!(res instanceof Scaler))
throw new ParseException("det: result must be a scaler");
if(!(lhs instanceof Matrix))
throw new ParseException("det: argument must be a matrix");
Matrix mat = (Matrix) lhs;
if( mat.getNumRows()!= mat.getNumCols())
throw new ParseException("det: argument must be a square matrix "+mat);
if(mat.getNumRows() == 2)
{
res.setEle(0,sub.sub(
mul.mul(mat.getEle(0,0),mat.getEle(1,1)),
mul.mul(mat.getEle(1,0),mat.getEle(0,1))));
}
else if(mat.getNumRows() == 3)
{
// | a b c |
// | d e f | -> a e j + b f g + c d h - a f h - b d i - c e g
// | g h i |
Object r1 =
mul.mul(mat.getEle(0,0),mul.mul(mat.getEle(1,1),mat.getEle(2,2)));
Object r2 =
mul.mul(mat.getEle(0,1),mul.mul(mat.getEle(1,2),mat.getEle(2,0)));
Object r3 =
mul.mul(mat.getEle(0,2),mul.mul(mat.getEle(1,0),mat.getEle(2,1)));
Object r4 =
mul.mul(mat.getEle(0,0),mul.mul(mat.getEle(1,2),mat.getEle(2,1)));
Object r5 =
mul.mul(mat.getEle(0,1),mul.mul(mat.getEle(1,0),mat.getEle(2,2)));
Object r6 =
mul.mul(mat.getEle(0,2),mul.mul(mat.getEle(1,1),mat.getEle(2,0)));
Object r7 = add.add(r1,add.add(r2,r3));
Object r8 = add.add(r4,add.add(r5,r6));
res.setEle(0,sub.sub(r7,r8));
}
else
{
Object[][] m = mat.getEles();
res.setEle(0,det(m));
}
// throw new ParseException("Sorry can only calculate determinants for 2 by 2 and 3 by 3 matricies");
return res;
}
/** returns a matrix excluding the specifyed row and column */
public static Object[][] dropRowCol(Object[][] mat,int xrow,int xcol)
{
int nrows = mat.length;
int ncols = mat[0].length;
Object res[][] = new Object[nrows-1][ncols-1];
int currow = 0;
for(int i=0;i