Changeset 25439

Timestamp:

Sep 18, 2009, 9:20:23 AM (17 years ago)

Author:

Paul Price

Message:

Fixing fuzz so that the expectation value is preserved: by adding
random values on [0,l), was effectively adding 0.5 to the background.
The proper range is [-0.5,0.5).

File:

• trunk/psLib/src/fits/psFitsScale.c (modified) (1 diff)

trunk/psLib/src/fits/psFitsScale.c

@@ -319 +319 @@
                     value = (value - zero) * scale; \
                     if (options->fuzz) { \
-                       /* Add random factor [0,1): adds a variance of 1/12, */ \
+                       /* Add random factor [-0.5,0.5): adds a variance of 1/12, */ \
                        /* but preserves the expectation value */ \
-                        value += psRandomUniform(rng); \
+                        value += psRandomUniform(rng) - 0.5; \
                     } \
                     /* Check for underflow and overflow; set either to max */ \