Red Hat Bugzilla – Bug 79845

Package info (from rpmquery -i) incorrect

Last modified: 2005-10-31 17:00:50 EST

Description of problem: The 'units' package description states that the program "can only handle multiplicative scale changes" whereas the man page states that that is not the case, and even gives an example (which works) to contradict that. Version-Release number of selected component (if applicable): 1.74-4 How reproducible: rpmquery -i units Actual results: "Units can only handle multiplicative scale changes (i.e., it can not tell you how to convert from Celsius to Fahrenheit, which requires an additive step in addition to the multiplicative conversion)." Expected results: "The `units' program can handle multiplicative scale changes as well as nonlinear conversions such as Fahrenheit to Celsius."

Farenheit to Celsius definitely _is_ linear. It's just y = Ax +B.

The point, in case it wasn't clear enough already, is that the two texts are contradictory, and that the package description would lead one to believe that it cannot be used for that type of conversion -- whereas it can.

fixed in 1.80-3

A linear transformation T has the property that T(x+z)=T(x)+T(z). (That's part of the definition of linear transformation.) If you try your form T(x)=ax+b you'll find that T(x)+T(z)=ax+b+az+b=a(x+z)+2b but T(x+z)=a(x+z)+b. So the property does NOT hold, and hence the form T(x)=ax+b is NOT a linear transformation. The Fahrenheit to Celsius transformation y=ax+b is an affine transformation. http://mathworld.wolfram.com/LinearTransformation.html http://mathworld.wolfram.com/AffineTransformation.html http://algebra.math.ust.hk/matrix_linear_trans/02_linear_transform/lecture3.shtml http://www.instantweb.com/foldoc/foldoc.cgi?affine+transformation

*** Bug 100404 has been marked as a duplicate of this bug. ***