I think the javadoc for RealMatrix.subtract is wrong. It says "@return this + m", which perhaps should be "@return this - m"
Index: src/main/java/org/apache/commons/math/linear/RealMatrix.java
===================================================================
— src/main/java/org/apache/commons/math/linear/RealMatrix.java (revision 799902)
+++ src/main/java/org/apache/commons/math/linear/RealMatrix.java (working copy)
@@ -60,7 +60,7 @@
- Compute this minus m.
*
- @param m matrix to be subtracted
- * @return this + m
+ * @return this - m
- @throws IllegalArgumentException if m is not the same size as this
*/
RealMatrix subtract(RealMatrix m) throws IllegalArgumentException;
thanks for the report