plotting a symbolic function
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i need to create symbolic function f(x) equalling ((3*x-5)/(x-3))
then make symbolic equation, invEqn, by setting x equal to f(y).
solve function to solve invEqn for y and use expression to define the symbolic function finv(x)
Plot f and f^-1 on the same axes.using fplot.
can someone write me a code not sure where to start
Risposte (1)
Cris LaPierre
il 20 Ott 2020
Modificato: Cris LaPierre
il 20 Ott 2020
2 Commenti
Walter Roberson
il 20 Ott 2020
The first parameter to fplot() must be a symbolic expression or symbolic function or function handle.
The second parameter to fplot() must be the range to plot over.
invEqn = x == f(x);
No,
invEqn = y == f(x);
which you need to solve for x, and the result needs to be a function of y, not a function of x (watch out for what you assign the output to!)
Note: it happens that for functions of the form (A*X-B)/(x-A) that the solution is x = (A*Y-B)/(Y-A) -- just replacing the X with Y. If you plot over the same range, you are not going to be able to tell the functions apart.
This is not something that happens in general, only for that special form. If it were (A*X-B)/(x-C) then the solution would be (C*Y-B)/(Y-A) with the constant having moved from the denominator to the numerator... but your constants are the same between numerator and denominator.
Rik
il 21 Ott 2020
Deleted comment:
done this so far:
syms y x f(x) finv(x)
f(x) = ((3*x-5)/(x-3)) ;
Eqn = f(x)==((3*x-5)/(x-3));
invEqn = x == f(x);
finv(x)=invEqn;
fplot(x,f(x))
fplot(x,finv(x))
but its not plotting the graphs opens a blank graph and keeps giving me errors
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