# Stefan Wehmeier

### MathWorks

Working on the symbolic toolbox, mostly in the MuPAD language. Responsible for solvers and simplifiers.

Professional Interests: computer algebra

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**Content Feed**

How to stop MATLAB livescript from simplifying the answer?

Use sympref('AbbreviateOutput', false)

4 years ago | 3

| accepted

These equations have an answer - how to get solve to find it?

Why not just solve(expression1 == expression2, u) ? What you did is to confuse assignemnts/assumptions with equations. You ...

4 years ago | 0

Function Iteration for n times, but n is NOT a fixed number

Why don't you make your last source code the body of a function? Is l at any time called with non-constant argument, such that y...

4 years ago | 0

an error in new versions? triognometric function of A*t

It is a matter of taste if you prefer results in terms of exp or sin. You could do simplify(rewrite(A1, 'sin'))

4 years ago | 1

| accepted

Symbolic toolbox mpower unexpected behaviour

You can use symbolic N but not in connection with mpower. As T^N = exp(N*log(T)), write TN = expm(N*logm(T)) and procee...

5 years ago | 1

| accepted

mupad command calling from matlab produce wrong results

I cannot reproduce this. In any case, you cannot work with intervals in MATLAB; this is why poles(f) gives you just the ...

5 years ago | 0

Why does eig(A) not return a symbolic array for my symbolic matrix A?

The roots of polynomials of degree > 4 usually do not have a symbolic representation. The same holds for eigenvalues as they are...

7 years ago | 0

| accepted

Parametric solutions to system of equations inequations via solve()

I see that you are using R2014a. Then your only option is to solve for one variable solve(e(1) == 0, a) and take this as...

7 years ago | 0

| accepted

subs(a,b,1) introduces variable b into a?

I cannot reproduce this. If it happens (in which version ??), then it is clearly unexpected.

7 years ago | 0

Problems with matlab symbolic dsolve function

The correct syntax is syms y(x) dsolve(diff(y, x, x) +y==x*exp(-x^2)) as it declares y as a function of x (and not of...

7 years ago | 0

Matlab 2012b too slow when solving a system of two equations on mupadmex(statement)

A running time of one hour can be normal if the equations are very complicated. Since your code does not run as it stands, it is...

7 years ago | 0

Symbolic array pre-allocation

My question is in which form do you have the 50000 entries you want to fill in. As strings in a cell array A? Then B = cell...

7 years ago | 0

| accepted

Find conditions such that symbolic expression is real-valued

a) feval(symengine, 'solve', a*x^2 + b*x + c, x, 'Real', 'IgnoreSpecialCases') You may omit the IgnoreSpecialCases, whic...

10 years ago | 0

| accepted

simplifying symbolic expression in terms of other variables

You could also try syms a b x assume(x== a+b); F = a^2+b^2+2*a*b+a+b+1; simplify(F)

10 years ago | 2

| accepted

Can you turn off all simplifications?

It's a bit tricky. hold(4/6) will not help you because 4/6 -> 2/3 is done by the parser. You will have to define "frozen" forms ...

10 years ago | 1

Square root of a polynomial over gf

You will have to do it by hand, that is, use polylib::sqrfree and divide all multiplicities by 2. These multiplicities are in th...

10 years ago | 0

| accepted

Factorize transfer function

Don't know how to do it using tf, but you can do syms s Suu = -1.6/((s-4)*(s+4)) Sux = -0.8/((s+4)*(s-4)*(s^2 + 0.1*s...

10 years ago | 1

| accepted

How to solve this equation

This is a recurrence equation and thus has to declared as such using rec(...). eq = evalin(symengine, 'rec(f(x)=h0*f(x)+h1...

10 years ago | 0

irreducibility test

You have to declare it as a polynomial over GaloisField, e.g. F = evalin(symengine, 'poly(x^2-2, Dom::GaloisField(5^7))) ...

10 years ago | 2

Problem Solving Symbolic Inequalities

Note that by default solve is in complex mode, i.e., you are looking for all solutions within the complex numbers. Try solu...

10 years ago | 0

| accepted

Symbolic substitution to eliminate variables without solving for the explicit expressions

The second system, too, can be solved. You will have to work on the MuPAD Notebook level or use feval(symengine, ...) though bec...

11 years ago | 1

| accepted

Solving a sine-cosine equation ( Warning: Explicit solution could not be found.)

There is no closed-form symbolic solution for general n, and for given n nobody can say which solutions are between -5 and 5 wit...

11 years ago | 0

"solve" cannot find analytic solution to a large multi-equation system, unless one is willing to break up the system and solve the parts sequentially

Hi Tamas, this works in newer versions of the symbolic toolbox (R2011a) as we have added some heuristics for systems containing...

11 years ago | 1

| accepted