Units Conversion Toolbox

This toolbox attaches units to Matlab variables and enables unit conversion.

Description

Have you ever needed to convert horse power to watts but can't remember the conversion factor? How many inches light travels in a microsecond? This toolbox is designed to make getting these answers much easier.

The "unit" statement attaches units to a variable. For example,
>> x=unit(2,'yards')
 
x =
     1.8288 m

returns the answer in International (SI) units. If you would rather have you answer in feet it can be converted to feet by

>> convert(x,'feet')
 
ans =
     6 feet

Variables created by the "unit" statement can operated on by these operators:

      Unary plus, Unary minus, +,-,*,.*,/,\,./,.\,^,.^,',.'
      and sqrt

Variables are also supported by triginometric,hyperbolic, and exponential functions and can be compared by

       ==, ~=, >, <, >=, and <=

Special plotting routines are available for plotting variables with units. These are:

      plot, semilogx, semilogy, and loglog

The toolbox appears in the html help screens and has "GettingStarted', "User Guide", and function help screens.

Just down load the tool box to the directory of you choice and set the Matlab path to include this directory. To verify operation, type

>> unit('yards')
 
ans =
     0.9144 m

If you get this result, you are all set!

• Acknowledgements: This submission has inspired the following:; Unit Converters
• MATLAB release: MATLAB 7.11 (2010b)
• Other requirements: none

[Erich]

In MATLAB R2011b I get:

>> Units(3, 'ft')
Error using Units
Error: File: Units.m Line: 1 Column: 10
Naming a class 'Units' is not allowed, because it is already a built-in class.

[Erich]

Very easy to work with units using this toolbox. Author quickly updated the files when R2011b introduced an incompatibility.

[John]

This is a great toolbox to have handy but it seems to have problems with vectors and arrays of objects. For example, (I am running MATLAB 2010b):

>> a = [unit(1,'m') unit(2,'m')]
 
a =
??? Error using ==> plus
Too many input arguments.

Error in ==> unit>unit.display at 1827
                s=sprintf(' %g %s',x.value+x.offset,x.name);

But when I change it to

>> a = [unit(1,'m') unit(2,'m')];

there is not issue. It seems the call to sprintf is having trouble with multiple inputs.
Overall this printing issue is not what concerns me, it is when I try to perform an operation on this array when I really run into trouble:

>> a * unit(1,'m')
??? Comma separated list must have exactly one item.

Error in ==> unit>unit.unit at 163
                    if U.hasBeenConverted

Error in ==> unit>unit.mtimes at 387
                A=unit(A);B=unit(B);

I was hoping to get back a <1x2 unit> where both values are now in m^2. I run some highly vectorized code and it was be great if this issue could be resolved, overall great toolbox. Thanks

[Michael Katz]

 

[Erich]

Try
>> a= unit([1 2],'m')

[John]

Thanks Erich, that works perfectly

[Collin]

Great toolbox.

Ran into a small problem with non-dimensional unit's plus and minus (unit class with .name = ''). I fixed the problem by replacing all the

  if A.name == B.name
        ......
  end

with

    if strcmpi(A.name,B.name)
         ......
    end

as ''=='' is an empty matrix

[Collin]

 

[Ronan CIMADURE]

Perfect :)

[Marco]

can you add this function to the unit class? Some formulas has absolute value in them, and I need to preserve units.

function C=abs(A)
A=unit(A);
C=A; C.value=abs(A.value);
end

[Marco]

I cannot use this toolbox to find roots of polynomial using the roots function when coefficientes are unit-class type. I first have to define a isfinite function in the unit class, but then I have problems with the transpose and ctranspose function I am unable to solve myself. Can someone help?