Items tagged with units


I am trying to use the element properties Maple has in its ScientificConstants package. I am running into problems with the density of gaseous elements:


Units:-UsingSystem(); # returns SI as expected

GetValue(Element('Si',density)); # returns 2329.0000 [kg/m^3] which is 2.329 g/cm^3, which is correct

GetValue(Element('H',density(gas))); # returns 88 [kg/m^3], which is incorrect.

PDG gives the density of hydrogen as 8.376E-5 g/cm^3, which is 0.08376 kg/m^3.  

Even more crazy for Krypton:

GetValue(Element('Kr',density(gas))); # returns 3677.000 [kg/m^3]. Heavy little buggers, these Kypton atoms! Should be 3.486 in the same units.

What gives? Am I missing something here?

Mac Dude



I am new to Maple and I am trying to add units to the "Flow Through an Expansion Valve" Application Demonstration.  I was trying pressure in [PSI], temperature in [degC] and flow rate in [kg/hour] everything else in SI units.  I included with(Units:-Standard) but had no luck with the fsolve function.

Any chance someone could make a version of this demonstration applicaton that includes units?





how can I tell Maple that "u" has the dimension of volts? 

Thanks for every good advice.


Not to long ago i found a post showing that maple was able to show the steps behind math.


   (convert(expr,name) =
   = eval(expr):
end proc:



                     (a+b*c = 1 + 3*5) = 16

However if I assign a unit to any of these numbers (a,b or c), the twostep code won't work.

Is there any way that maple can show the steps, while having it both show and convert the units?



b:=40Ohm:   (I can't insert the Omega sign)

c:= twostep(a/b);

                (a/b=70V/40Ohm) = 1,75A


I was wondering if it is possible to use units in Maple so I can always check if the result I have at the end of calculation is the meter.  For example:


The answer is of course 3.10^8 m^3*kg/s^3

I try to do something with the units but I am unable to crreate something that will simplify the m/s ffactor to 1.

Any idea?

Thank you in advance for your help.


Funny, I can't seem to find a list of all available units in the help file.

Is there not a listed table of units somewhere?

**edit add**  conversion of units I mean.  ie.  meters, miles, gallons, litres, Pa, etc...

Im attempting some very basic calculations where numbers are stored in variables with correct units. However i wish to take a variable to the power 2 without altering it's unit. This is a really easy but strange calculation to make which is why i guess Maple is having trouble with it. 

e.g. I have a variable A with a number 4 stored inside with unit in Meters. I want to take A2 = 16 meters and and not A2 = 16 meters2

Is there a function or way to select the base number without having to write an entire line about it? 


can do the trick but i believe there has to be an easier, less complicated, way to achieve this? 


im currently using Mathcad 15 and i want to change to a newer and better software with more possibilities.

But up to now i have not found a better software for calculating. One big advantage with mathcad is the possibilitie of symbolic formula input and calculation with units.

Now my question: Is it possible with Maple to write symbolic formulas (2D Structure of big formulas)

I dont write a formula in one row. Its nearly impossible ...

And can i calculate with units?

Thx Stefan


Hi there,

I was wondering how to define the unit of an unspecified function. Here is what I want to do:

Say I have the coordinates of a Point in 1D-Space denoted by an unknown function x(t). While this function depends on time t the value of this function is supposed to be of SI Unit meter.

When calculating diff(x(t),t) I would like to get something like (absolut derivative of x(t)) * Unit(m/s).

So how do i tell maple that x(t) is something like f: time -> meter?
Also: How to specify that t has unit second without breaking the diff() command?

Any help would be greatly appreciated.



I tried to generate a simple plot based on an expression using units. Please see the screenshot of the worksheet below

The y-axis should be scaled in m3 not m2 because a, b and the variable r are in m. I know that it is possible to enforce the axis scaling in units using useunits but since the mathematical definition of the expression is clear this should not be necessary.

The other question is why is the y-axis missing the variable name? On this page on the Online Help it is mentioned "When you plot an expression, the axes labeling shows the variable names and units." I think what I am plotting is an expression.


I understand that if I want to use a scientific constant in a Maple worksheet or document, I first have to declare it. Here is an example for the speed of light:

However if this worksheet is re-executed (e.g. using !!!) this happens:

Obviously there is a kind of recursion for c which is listed in the Variable Palette as a name for a variable but which is also the scientific constant. The problem can be solved e.g. by associating another name to the constant and unassigning the old definition in the Variable Palette:

This works but it makes the document harder to read since everybody is used to lowercase c for the speed of light. The same is of course true for other scientific constants.

Is there a way to use scientific constants in their "usual" notation in Maple, including using the unit of the constant?

When using units, then e.g. "2 m" is show as expected below, but "1 m" shown as only "m".  Even through correct, it is a non-standard way to write physical values.

How to get the physical values in a format of "{numerical} {unit}" even when the numerical part is 1?

In a simple example below I try to write an equation with an unknown value present among other values that have unit, but I get an error since the unknown value d does not have a unit yet.

How to write such expressions, e.g. for use in solve later?



Below I try to use units for a simple expression, where "m" and "mm" is added on Windows using Ctrl-Shift-U.

Why does the value with unit "1 [[m]]" not show as "1 m" in (1), but simply as "m" ?

Why does the addition not result in "2 m" ?

At least I had expected the addition to be made when using "evalf()".


Dear Maple users

I wanted to use the zip-command to muliply two lists with units. It works without units, but not with units:



If I add units to each entrance it works too, but not very convenient. How is it done with units in the best way?




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