On Aug 2, 10:47 pm, William Stein <wst...@gmail.com> wrote: > 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). >
cvxopt matrices (you can use them in Sage if you like) have .T attribute. > 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 > > athttp://groups.google.com/group/sage-devel > > URL:http://www.sagemath.org > > -- > William Stein > Professor of Mathematics > University of Washingtonhttp://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
