Questions about calculating with units in Mathematica.

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29
votes
4answers
2k views

Are Mathematica 9 units really slow?

This generates 75 unitized pairs for a plot that displays physical units: ...
3
votes
1answer
93 views

Wavelength, wavenumber, energy and frequency in a ruler

I would like to generate set of four axis relating wavelength, wavenumber, energy and frequency in an arbitrary range. Like in this image but without the labels such as "RADAR". The selection of ...
2
votes
0answers
53 views

Quantities formatting problem

So I've developed this simple code ...
0
votes
0answers
52 views

Meaning of backtick in conjunction with units [duplicate]

In this fragment from an equation solution the backtick is used twice: ...
0
votes
0answers
42 views

Fitting data involving units

I want to fit some data to a model. However, if the data involves units in the independent variable, fitting seems not to work. As an example, consider the code ...
2
votes
4answers
92 views

Cancelling units in two-argument ArcTan

Consider ArcTan[3, -3] (* out: *) -Pi/4 ArcTan[3 a Sin[t/2], -3 a Sin[t/2]] (* out: *) ArcTan[3 a Sin[t/2], -3 a Sin[t/2]] However, we can fix the ...
0
votes
0answers
33 views

FindRoot with units error: Message text not found

This is sort of embarrassing. I'm working on a document to extol the virtues of Mathematica, and I can't get it to solve a relatively simple system of equations involving units. In this code, when I ...
0
votes
1answer
79 views

AstronomicalData not including units?

I like using mathematica to do my physics homework, and AstronomicalData is useful for that, but it doesn't seem to work properly with units. [the question is, at ...
-1
votes
2answers
108 views

Why won't Mathematica work with quantities or Quantity[]? [closed]

As you can see in the screenshot below, Mathematica is simply not evaluating any quantities. It is simply listing them as I wrote them. Could anybody give me a pointer as to why this may be?
2
votes
1answer
172 views

UnitSimplify returns unexpected non-SI unit combination

I am trying to get units working in mathematica in the following expression for diffusion: $D = {K_B T}/{3 \pi \eta L}$ My code is as follows: ...
7
votes
3answers
402 views

Suppress connection to Wolfram|Alpha when making unit conversions

I want to speed up calculations with unit conversions. I suspect primarily that some units evaluate from Wolfram|Alpha. Any way to prevent this automatically, so that Mathematica throws ...
25
votes
7answers
2k views

Simpler input for the new unit support

I've been playing with the new unit support in Mathematica 9. It seems very useful, but the syntax is very verbose. Instead of typing: ...
-1
votes
1answer
72 views

Make Quantity behave reasonable with Degrees Celsius

When using a Quantity with the unit of "DegreesCelsius" multiplication doesn't work as expected. If you have 10 degrees and ...
3
votes
1answer
91 views

Choosing the units for plotting

I´m new to using units in Mathematica. I have read other similar posts about this issue but I haven´t found an answer so far. My problem is simple: I want to plot a certain function with a certain ...
1
vote
1answer
87 views

Multiplying SI Prefixes [closed]

I'm doing a few calculations and would like to keep my units straight. I figured that using the built-in Units functionality could help with this. However, using SI prefixes doesn't seem to give the ...
1
vote
1answer
176 views

Unit of the frequency axis in BodePlot

I have a simple question: What is the unit of the frequency axis in the BodePlot? I searched the documentation, but only found this: The scaling functions can be specified as ...
1
vote
0answers
118 views

How can I say that all quantities need to be positive (and real)? [duplicate]

Can you say at the beginning of a script in Mathematica that you want all the quantities to be positive (and real)? So that in all calculations, only the real values of these quantities will be ...
4
votes
2answers
206 views

Using units and piecewise functions in Integrate

For simple cases, Quantities appear to be handled well by Integrate: ...
1
vote
1answer
82 views

Grouping units more sanely

Would it be possible to get Mathematica to group units more sanely. For example the calculation: ...
5
votes
0answers
133 views

Units: Custom-defined units possible?

Converting between revolutions per minute (RPM) and revolutions per second (RPS) is not straightforward for me in Mathematica. I know that $1\; \text{RPM} = \frac{2\; \times\; \Pi\; ...
1
vote
1answer
195 views

How to get the quantity of Physical constants?

I need to get the quantity of gravitational constant: QuantityMagnitude[GravitationalConstant] why this is not work? Already load the ...
1
vote
1answer
100 views

Caching data in Mathematica package

Consider the following: m=Quantity[1,"meter"] If I run the package, it will return 1m But when I load the package, the ...
10
votes
1answer
316 views

Kelvin per Kelvin Difference

I'm trying to use Mathematica units more often, but I've run into the following problem: ...
3
votes
1answer
205 views

Why cant Mathematica 9 interpret this unit?

I'm using Mathematica 9.0.1. Sorry for using an image, but pasting code messed up the output formatting. I'd like to represent 25 Btu/(hr ft F). All units are spelled correctly as identified in ...
2
votes
0answers
71 views

Is it possible to use Gaussian cgs units in $Mathematica$ computations?

I was trying to do computations in Gaussian cgs units, and of course I failed due to dimensional issues. For instance, $q_1 q_2/r$ cannot be converted to $\mathrm{erg}$ since Gaussian system uses ...
2
votes
1answer
272 views

Problem in units convertion when multipliying Boltzmann constant and a temperature

When define the temperature of a variable in Celsius, Mathematica 9.0 does not calculate the right answer when multiplying by boltzmann constant. Example: ...
6
votes
3answers
161 views

Can't force UnitConvert to be evaluated in Plot

I'm trying to use new units support in Mathematica 9. When I Plot Quantity functions everything is OK. ...
5
votes
0answers
91 views

Moles/Liters doesn't get simplified to Molar even though Molar*Liters gets simplified to Moles

Why can't Mathematica 9 simplify mol/L to M, when it can simplify M*L to mol? ...
4
votes
2answers
312 views

Why doesn't Mathematica divide out the Kelvins?

I thought I understood Mathematica V9 units. However, I can't get these numbers to plot, or even to come out to a nice clean unit of mass (say grams). The Kelvin's ...
1
vote
1answer
63 views

Extract function parameters from “unevaluated” FormBox

I want to get the abbreviation for a Unit from its full name eg. "Newtons" => "N". Using ...
1
vote
0answers
80 views

Insert a Quantity Unit literal in TraditionalForm

Is there a keyboard shortcut for creating something like the result of this: Quantity["Kilograms" * ("Meters")^2 / ("Seconds")^2] After copying the result to a ...
3
votes
2answers
470 views

Units, plotting and empty plots

maybe I'm completely newbie but I can't understand the behavior of units and the command plot. I'm doing some easy plotting of the state equation for gasses: ...
1
vote
0answers
55 views

Will aliasing the Quantity and UnitConvert functions to “in” and “to” create problems?

It seems that there is a lot of interest in enhancing the use of units in Mathematica; various solutions in the name of brevity, correctness, and general utility have been demonstrated. I've begun ...
13
votes
2answers
466 views

Built-in unit strings recognized by Quantity?

It’s great that Quantity can utilize Wolfram Alpha to interpret unit strings that it doesn’t recognize, but I need my code to work on machines that do not have Internet access. Is there a complete ...
10
votes
5answers
702 views

Implementing CGS unit system in Mathematica 9

So I've just installed the trial version of Mathematica 9. The first noticeable feature for me is the new built-in physical units. I used AutomaticUnits package ...
0
votes
1answer
164 views

Cannot convert units in Mathematica [closed]

One of the big things Wolfram touted about their new mathematica 9 was its ability to format units, and do calculations with them. I however can't seem to find out how to actually use them to ...
10
votes
1answer
300 views

How do I seamlessly migrate from the older Units package to Mathematica 9's Quantity objects?

I have several notebooks that make use of the Units package and would like to be able to work simultaneously with the older units and ...
5
votes
0answers
143 views

Quantity and Trig functions

I have a bunch of data to which I've assigned units using Quantity, including some angular measurements in degrees. I'd like to be able to use these measurements ...
5
votes
1answer
244 views

Getting all physical units with prefixes

How we can get the list with all physical units and prefixes from WolframAlpha and make symbols from the result to be equal their corresponding quantities like described in this post?
2
votes
0answers
71 views

List of supported units in Mathematica 9 [duplicate]

Is there a list of supported units in Mathematica 9 documentation? I personal haven't found any; even the physical constants (newly supported as units in 9) can only be found in compatibility ...
1
vote
1answer
687 views

Plotting with Units

I'm trying to get Mathematica to plot with units, but I'm having some trouble. Below is a minimal example of trying to plot y = x, where ...
8
votes
1answer
252 views

Cannot plot Quantity values with DateListPlot

Is there a way to use DateListPlot with Quantity values? I retrieved the following time series data from WolframAlpha: ...
3
votes
3answers
225 views

How to deal with units in logarithms?

I'm trying to take a formula, take it's integral which yields a formula with logarithms, and then directly plug in values with units and get an answer. However if the units go into any of the ...
4
votes
1answer
132 views

NumberForm and units

NumberForm can be used to print Quantities to a specified precision. For example, x=Quantity[5.123456789,"Meters"]; 5.12346 m Print[NumberForm[x,{4,2}]] 5.12 m ...
14
votes
1answer
344 views

Unexpected behavior of UnitConvert

When I evaluate this expression: ...
6
votes
0answers
313 views

Incomplete implementation of units?

I've been playing around with the new units capability in MMA9 and I'm becoming a bit frustrated with what I perceive as an incomplete implementation of this capability and I'm wondering if there are ...
9
votes
1answer
902 views

Is there a “No Units” (i.e., dimensionless) unit?

I would like to be able to call the Quantity function with a null unit so that it returns the original dimensionless value. For example, ...
3
votes
1answer
513 views

Unit issues in Mathematica 9

I posted the following on the Google+ group comp.soft-sys.math.mathematica and had no luck with responses. I've done a Google search and, to the best of my ability, ...
2
votes
2answers
497 views

Use of own unit abbreviations

I have been using AutomaticUnits in my calculations. In this package all I had to do was to declare the units I wanted e.g. mm, kN, sec, kPa, litres etc. in terms of existing units, and then use them ...