setp SciMax Toolbox setup_autoload

SciMax Toolbox >> setunits

setunits

Maxima Function

Calling Sequence

setunits (list)

Description

By default, the unit package does not use any derived dimensions, but will convert all units to the seven fundamental dimensions using MKS units.

(%i2) N;
                                     kg m
(%o2)                                ----
                                       2
                                      s
(%i3) dyn;
                                   1      kg m
(%o3)                           (------) (----)
                                 100000     2
                                           s
(%i4) g;
                                    1
(%o4)                             (----) (kg)
                                   1000
(%i5) centigram*inch/minutes^2;
                                  127        kg m
(%o5)                       (-------------) (----)
                             1800000000000     2
                                              s

In some cases this is the desired behavior. If the user wishes to use other units, this is achieved with the setunits command:

(%i6) setunits([centigram,inch,minute]);
(%o6)                                done
(%i7) N;
                            1800000000000   %in cg
(%o7)                      (-------------) (------)
                                 127            2
                                            %min
(%i8) dyn;
                               18000000   %in cg
(%o8)                         (--------) (------)
                                 127          2
                                          %min
(%i9) g;
(%o9)                             (100) (cg)
(%i10) centigram*inch/minutes^2;
                                    %in cg
(%o10)                              ------
                                        2
                                    %min

The setting of units is quite flexible. For example, if we want to get back to kilograms, meters, and seconds as defaults for those dimensions we can do:

(%i11) setunits([kg,m,s]);
(%o11)                               done
(%i12) centigram*inch/minutes^2;
                                  127        kg m
(%o12)                      (-------------) (----)
                             1800000000000     2
                                              s

Derived units are also handled by this command:

(%i17) setunits(N);
(%o17)                               done
(%i18) N;
(%o18)                                 N
(%i19) dyn;
                                    1
(%o19)                           (------) (N)
                                  100000
(%i20) kg*m/s^2;
(%o20)                                 N
(%i21) centigram*inch/minutes^2;
                                    127
(%o21)                        (-------------) (N)
                               1800000000000

Notice that the unit package recognized the non MKS combination of mass, length, and inverse time squared as a force, and converted it to Newtons. This is how Maxima works in general. If, for example, we prefer dyne to Newtons, we simply do the following:

(%i22) setunits(dyn);
(%o22)                               done
(%i23) kg*m/s^2;
(%o23)                          (100000) (dyn)
(%i24) centigram*inch/minutes^2;
                                  127
(%o24)                         (--------) (dyn)
                                18000000

To discontinue simplifying to any force, we use the uforget command:

(%i26) uforget(dyn);
(%o26)                               false
(%i27) kg*m/s^2;
                                     kg m
(%o27)                               ----
                                       2
                                      s
(%i28) centigram*inch/minutes^2;
                                  127        kg m
(%o28)                      (-------------) (----)
                             1800000000000     2
                                              s

This would have worked equally well with uforget(N) or uforget(%force).

See also . To use this function write first load("unit").

setp SciMax Toolbox setup_autoload