# [sdiy] OT: Mathcad users?

Neil Johnson neil.johnson71 at gmail.com
Mon Sep 16 11:07:05 CEST 2013

```Hi,

"MATLAB" is, as Olivier says, mainly a matrix tool, hence the name:
"MATrix LABoratory".  It, and its clones Octave (text-based) and
SciLab (GUI-based), are the main tools used where the problem can be
described as a matrix, such as an audio sample, 2D image, a set of
vectors, and so on.  I've professionally used Matlab for image
processing, speech recognition, magnetic sensor development, digital
filter design, optical modelling, amongst others; personally I've used
Octave for exploring ideas in digital waveform synthesis.  Great for
crunching numbers and making matrices dance.

At the other end of the spectrum you have symbolic manipulation
programs like Mathematica, MAPLE, MathCAD, and free versions such as
Maxima (wxMaxima provides a GUI front end), Sage (which is built on
top of maxima), and so on that deal with symbolic mathematics.  They
understand equations, how to transform equations, solve them, they
know things like trig identities, integration, differentiation, all at
the symbolic level.  I've used maxima for exploring analogue filter
designs, as you can pretty much type in the equations describing state
variable filter outputs, solve to get the transfer function, and then
plot the phase and magnitude responses.  Not so good at crunching
large data sets though.  There is also an online web version of maxima
that can be useful for quick checks or for sharing; here is one
example during a discussion about a filter design (sorry about the
long URL):

http://maxima-online.org/index.html#?in=eq1%3A%20Vint%3D-Iint%2F%28s*C%29%3B%0A%0Aeq2%3A%20Iint%3Dk*Iin%3B%0A%0Aeq3%3A%20Iin%3DVin%2F30000%20%2B%20Vint%2F30000%3B%0A%0Aeq4%3A%20Iout%3DVint%2F15000%2BVin%2F30000%3B%0A%0Aeq11%3A%20Vint2%3D-Iint2%2F%28s*C%29%3B%0Aeq22%3A%20Iint2%3Dk*Iin2%3B%0Aeq33%3A%20Iin2%3DIout%20%2B%20Vint2%2F30000%3B%0Aeq44%3A%20Iout2%3DVint2%2F15000%20%2B%20Vint%2F30000%3B%0A%0Aeq5%3A%20linsolve%28[eq1%2Ceq2%2Ceq3%2Ceq4%2Ceq11%2Ceq22%2Ceq33%2Ceq44]%2C[Iin%2CIout%2CVint%2CIint%2CIin2%2CIout2%2CVint2%2CIint2]%29%3B%0A%0Aeq6%3A%20rhs%28eq5[6]%29%3B%0A%0Aeq7%3A%20%28eq6%29%2CC%3D220e-12%2Ck%3D0.01%2Cs%3D%25i*2*%25pi*f%2CVin%3D1%3B%0A%0Aplot2d%28[360%2F%282*%25pi%29*carg%28eq7%29%2C20*log%28abs%28eq7*30000%29%29%2Flog%2810%29]%2C[f%2C1%2C100000]%2C[logx]%29%3B%0A%0A

Then there are the pretty printers and plotters, like the Word
Equation Editor, OSX's Grapher, the venerable gnuplot, and so on.
They're simpler tools, they don't do much, if any, thinking for you,
but they can produce nice output suitable for publication.  For
example, both octave and maxima use gnuplot for plotting duties.

Cheers,
Neil

On 16 September 2013 08:48, Olivier Gillet <ol.gillet at gmail.com> wrote:
> The Mat in Matlab is that of "Matrix", and not "Mathematics". It is
> primarily a numerical computation tool - to evaluate programs and
> expression on arrays of data - which makes it a tool of choice for
> signal and image processing. Its symbolic processing options (solving,
> manipulating algebraic expressions) are optional and not really what
> people are using the program for.
>
> Octave and Scilab are both open-source clones of Matlab. Both of them
> are incompatible with matlab code, which make them kind of pointless
> for serious work where one has to reuse reference implementations
> available as matlab toolboxes. They are OK for teaching though.
>
> I'm surprised no one has mentioned scipy - which is my tool of choice
> for numerical duties and plotting, from an iPython shell. For those
> who prefer IDEs and "Notebook" like interfaces, there's this ongoing
> project -> www.sagemath.org
>
> On Mon, Sep 16, 2013 at 4:34 AM, Dan Snazelle <subjectivity at hotmail.com> wrote:
>> Ive been noticing matlab code in more and more books on digital audio
>>
>> Does it also work as a self-teaching tool? Mathmatica seems like it might be good for exploring/learning math
>>
>> Sent from my iPhone
>>
>> On Sep 15, 2013, at 8:41 PM, rsdio at sounds.wa.com wrote:
>>
>>> It's nowhere near as powerful, but Apple ships Grapher with OSX. In Grapher, you can type equations and see them graphed alongside each other, in 2D or 3D. This is a great way to check out a new formula or even a circuit idea. I recently used Grapher to get an idea of the response from adding parallel resistance to the wiper of a pot (note, it's not linear). But there are many limitations compared to the huge environment of MATLAB or similar.
>>>
>>> Brian
>>>
>>>
>>>> Has anyone here used Mathcad http://www.ptc.com/product/mathcad ?
>>>>
>>>> Any thoughts, tips, probs, etc?
>>>>
>>>> I'll be using it as part of a course I'm doing so I don't really have a
>>>> choice regarding alternatives - but if you have a preference for something
>>>> similar I'd be interested to hear about it.
>>>
>>>
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