MATLAB: Expr2=collect(EXPR,’exp(-t)’) Why is it wrong

MATLABr2018bsymbolicSymbolic Math Toolbox

EXPR=str2sym('(x^2+x*exp(-t)+1)*(x+exp(-t))')

expr1=collect(EXPR)

expr2=collect(EXPR,'exp(-t)')

Why expr2 shows: sym.charToFunction (line 26) Invalid variable name

Best Answer

expr2=collect(EXPR,exp(-t)) % no single quotes around the second argument

Related Solutions

MATLAB: Symbolic collect and display

I am not certain what result you want.

Try this:

[cfs,trm] = coeffs(coeffs_cosy, cos(y))

producing:

cfs =
[ 4*sin(x), 4*cos(x)*sin(y), -3*sin(x), -cos(x)*sin(y)]
 
trm =
[ cos(y)^3, cos(y)^2, cos(y), 1]

Experiment with the coeffs arguments to get the result you want.

MATLAB: Does Maple return terms with a function “erfi” that cannot be understood by Symbolic Math Toolbox or MATLAB

The term erfi(x) is Maple's representation of the imaginary error function. There is no exact equivalent symbolic function in Symbolic Math Toolbox (the closest is the MATLAB function ERF in MATLAB).

To work with such expressions, convert the term erfi into terms that MATLAB can understand. From the Maple help this function is defined as,

 erfi(x) = 2/sqrt(pi) * int(exp(t^2), t=0..x)

You can use the following expression to convert this into a MATLAB symbolic expression

syms x t
myErfi=2/sqrt(pi) * int(exp(t^2),0,x)

Additional help for Maple can be found by typing

mhelp erfi

Note that Symbolic Math Toolbox uses MuPAD as its symbolic engine as of Symbolic Math Toolbox 5.1 (R2008b). Therefore, the MHELP function will not work if MuPAD is the active symbolic engine.

Best Answer

Related Solutions

MATLAB: Symbolic collect and display

MATLAB: Does Maple return terms with a function “erfi” that cannot be understood by Symbolic Math Toolbox or MATLAB

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