## linear_algebra Class QRTest_j

```java.lang.Object
|
+--linear_algebra.QRTest_j
```

public class QRTest_j
extends java.lang.Object

This class tests the (LINPACK) QR classes. It

1. Randomly fills an n by n matrix, X.
2. Randomly generates a vector b0.
3. Calculates the vector y = X(b0).
4. Performs a QR decomposition of X.
5. Solves the system Xb = y in an effort to recover b0.
6. Handles the regression equation y = a0 + a1*x + a2*x^2 + e where a0 = a1 = a2 = 1. Its estimates of the parameters should be close to 1. Its estimate of the standard deviation should be close to the input value.

 Constructor Summary `QRTest_j()`

 Method Summary `static void` ```isort(int[] x, int[] xsort, int[] origord, int n)``` `static void` `main(java.lang.String[] args)` `static double` `normi(double u)`            This is a normal cdf inverse routine.

 Methods inherited from class java.lang.Object `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

 Constructor Detail

### QRTest_j

`public QRTest_j()`
 Method Detail

### main

`public static void main(java.lang.String[] args)`

### normi

`public static double normi(double u)`

This is a normal cdf inverse routine. Created by Steve Verrill, March 1997.

Parameters:
`u` - The value (between 0 and 1) to invert.

### isort

```public static void isort(int[] x,
int[] xsort,
int[] origord,
int n)```