On Mon, Aug 2, 2010 at 1:38 PM, cousteau <cousteaulecommand...@gmail.com> wrote: > I'm studying engineering, and I'm used to some programs such as > Matlab, Maple, etc. When I knew about SAGE I found it very powerful, > simple and well structured, but I quickly found out that it wouldn't > be very useful in engineering, which is more oriented to numerical > analysis and simple math operations than to abstract algebra. Although > I could just use Octave for this, I'd like to be able to use SAGE for > some engineering-oriented tasks. Here are some proposed features: > > 1. ENGINEERING MODE > Since SAGE is oriented to mathematics, all numbers are considered > Integer unless otherwise specified (an integer is converted using > Integer() to SAGE's inner type). This isn't practical for engineers, > who normally use real numbers. > Solution: There should be a variable that caused all numbers to be > converted to RealNumber by default instead of Integer, even if an > integer was entered. >
You can make this happen as follows: sage: RealNumber=float; Integer=float sage: 2 + 3 5.0 sage: 4/7 0.5714285714285714 Note that this will screw many things up big-time, e.g., list indexing is broken: sage: v = [1,2,3] sage: v[2] --------------------------------------------------------------------------- TypeError Traceback (most recent call last) /Users/was/build/sage-4.5.1/<ipython console> in <module>() TypeError: list indices must be integers, not float > 2. UNITS > It would be nice to make SAGE capable of handling units and do unit > conversion. > Solution: There are already some Python modules that allow the "1 m" > syntax for a value with units. For some more complex units, I'd use a > syntax like "9.8 'kg*m/s^2' " (a literal number followed by a string), > or "9.8 [kg*m/s^2]" (a literal number followed by the units between > brackets). Sage already has extensive support for units. sage: kg = units.mass.kilogram; m = units.length.meter; s = units.time.second sage: a = (9.8 * kg * m / s^2); a 9.8000000000000007*kilogram*meter/second^2.0 sage: a.convert(units.mass.gram * m / s^2) 9800.0*gram*meter/second^2.0 > 3. BODE DIAGRAMS > I didn't find it easy to plot a Bode diagram of a function. The plot() > function doesn't appear to have a "logarithmic" option, and it doesn't > look easy to put 2 parallel plots on the same image, one on the upper > half and another on the lower half. > Solution: have a bode() function that does all the work (along with > nyquist() and maybe root_locus()). Extending the options on the plot() > function would also be nice (at least, add logarithmic_x and > logarithmic_y options). Parallel plots? Do you mean like this: sage: graphics_array([plot(sin(x), 0, 3), plot(cos(x),0,3)],2,1) > 4. MATRIX INPUT > SAGE lacks an easy way to enter matrices. The easiest one is to do > something like "matrix([[1,2],[3,4]])", but that's uncomfortable, > specially for people who are used to Matlab's (or Octave's) "[1 2; 3 > 4]". > Solution: My proposed syntax is "[[1,2],[3,4]]m", this is, a literal > list followed by an "m", as an alias to "matrix([[1,2],[3,4]])". Same > for "v" (vectors), "c" (complex numbers), maybe "q" (quaternions), > "p" (polynomials)... I think this is pretty easy: sage: matrix(2, [1,2, 3,4]) [1 2] [3 4] I don't like your suggestion to introduce something that isn't valid Python to enter matrices. > 5. MATRIX INDEXES > I had written a long paragraph about how easy is to get slices of > matrices on Matlab/Octave and how good it would be to implement > something similar on SAGE with some examples, just to realize that it > was already implemented. :( > (some examples: mat[3], mat[1,2], mat[0:3], mat[[3,2,1,0]], mat[:, > 0]...) Moreover, if you use numpy arrays you get extremely powerful and efficient slicing into n-dimensional arrays. This is very useful, e.g., when dealing with 3d scientific data. > > 6. TRANSPOSE/CONJUGATE > If I want to get the transposed of a matrix, I have to write > "mat.transpose()", while on Matlab it's as easy as "mat' ". Same for > conjugating complex numbers or transposing+conjugating complex > matrices. > Solution: The solutions are to have a .T (or .H, .C...) attribute, or > to have a custom operator that conjugates and transposes, such as > "*mat" or "+mat" (the latter might be easier to implement since > there's already an unary "+" operator in Python that doesn't do > anything useful). Why don't you do this: sage: T = lambda x: x.transpose() sage: A = matrix(3, [1,2, 3,4, 5,6]); A [1 2] [3 4] [5 6] sage: T(A) [1 3 5] [2 4 6] > > -- > To post to this group, send an email to sage-devel@googlegroups.com > To unsubscribe from this group, send an email to > sage-devel+unsubscr...@googlegroups.com > For more options, visit this group at > http://groups.google.com/group/sage-devel > URL: http://www.sagemath.org > -- William Stein Professor of Mathematics University of Washington http://wstein.org -- To post to this group, send an email to sage-devel@googlegroups.com To unsubscribe from this group, send an email to sage-devel+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-devel URL: http://www.sagemath.org
