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12-13-2013
08:46 PM

12-13-2013
08:46 PM

Lusk_Logspace Function and SigFigs.mcdx

UPDATE 2014-01-14: The attached .zip file now contains a Mathcad Prime 3.0 worksheet (.mcdx) and—for those of you who are still using earlier verisions of Mathcad—an Adobe Acrobat printout (.pdf) of the worksheet so can see how it is put together.

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One new and interesting Mathcad Prime 3.0 function is **logspace**. The purpose of **logspace** is to create a vector of logarithmically spaced points. The resulting vector is useful for creating log or log-log plots and for manipulating data that spans multiple decades. I learned about the new **logspace** function in Brent Maxfield's excellent new book Essential PTC Mathcad Prime 3.0.

As an engineer, I don't revel in unlimited decimal places and "messy" numbers except when it comes to fun things like **pi** and **e** and **sqrt(2)**. I am just old enough to have been an active part of the transition from slide rules (very limited precision) to the HP-35 and it's successors and to have had "significant figures" drummed into my head by my father (who was my high school chemistry teacher) and the late Mr. Lipston (my high school physics teacher, who was, unfortunately, afraid of RPN). The "sigfig" baton was then handed off to my engineering professors.

So, rather than use the initial **logspace** results, I would prefer to use values with a limited number of sigfigs, even though the number of sigfigs that is appropriate here is somewhat arbitrary. Unfortunately, rounding off to a fixed number of sigfigs in not built into Mathcad. Fortunately, it can be created in Mathcad.

The purpose of this worksheet, then, is to round off **logspace** results to a fixed number of sigfigs. This technique can be applied to other functions, but **logspace** saw it first.

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