How to improve the accuracy of drawing, especially for infinite functions？

in some plot assignments,we can use 'ezplot' to plot the more accurate figure but for infinite functions the 'ezplot' still can't plot it accurately,so how can we improve the accuracy of drawing, especially for infinite functions？

functions and codes are as this

syms m1;

g=9.8;
h=20;
hgang=20;
omega=2;

nu=omega^2*hgang/g;

g = @(m1) (i*m1)*tanh(i*m1)-nu;

fplot(g,[-10,20])
ylim([-60,40])

Answer 1

[Walter Roberson]

Use fplot() instead of ezplot()

And skip using inline(): inline() has been recommended against since MATLAB 5.1

[dcydhb dcydhb]

it seems that the 'fplot' has a Vertical bar which is not the figure of the function,so how to eliminate it?

thanka a lot!!!

[dcydhb dcydhb]

i accepted your answer but i still need your reanswer,thanks a lot!!!

[Walter Roberson]

In later releases, that vertical line is a dashed line of a different color.

[hasan s]

hello prof. Walter

please if possible

Is there a solution to the problem that the drawing contains

The vertical line is a dashed line of a different color

Is it possible to add a code to increase the accuracy of the drawing?

thanks alot

[hasan s]

Why does a straight line appear not straight?

Therefore, the professor's assessment in my exam to my solution is zero

[Walter Roberson]

The fplot() option 'Showpoles', 0 will turn off the dashed line.

f = @tan

f = function_handle with value:
    @tan

fplot(f, [0 10], 'showpoles', 0)

[hasan s]

thanks alot prof. walter for your reply

can I use 'showpoles', 0) with the

plot(x,f)

as

fplot(x,f, 'showpoles', 0)

what about the not straight line ???Still not straight line??

[Walter Roberson]

You cannot use showpoles with plot(). If you are using plot() then you need to detect the discontinuities yourself and deal with them.

When you have 'showpoles', 0 for fplot, the vertical line does not appear at all.

[hasan s]

thanks prof for your reply

I use plot

and the line figure not appear vertical

please look at your help in my question

https://ch.mathworks.com/matlabcentral/answers/851275-plot-a-lot-of-interval

the lines is not straight very well?? so the professor's assessment in my exam consider it wrong !

is there any way to improve the drwaing by adding code

[Walter Roberson]

If you have discontinuities and you want to use plot(), then you need to take one of two approaches:

1. Detect the discontinuities (somehow) and insert a nan at that location so that MATLAB stops drawing there; OR
2. Use your knowledge of the formulas to draw the lines in pieces, using hold on

If you use the Symbolic Toolbox and you write in terms of piecewise() then fplot() will detect the discontinuities and use vertical lines.

syms a b c d x real
part0 = piecewise(x<=a | x >= d, 0, 0);
part1 = piecewise(x>b & x < c, 1, 0);
part2 = piecewise(x > a & x <= b, (x-a)./(b-a), 0);
part3 = piecewise(x > b & x <= d, (d-x)./(d-c), 0);
f = part0 + part1 + part2 + part3

f = 

m = 10;
v1=unifrnd(0,1,1,m);
l1=unifrnd(0,1,1,m);
u1=unifrnd(1,2,1,m);
A = 0.1*l1';
B = 2*v1';
C = 3*v1';
D = 4*u1';

y = subs(f,{a,b,c,d}, {A,B,C,D});
fplot(y, [-1 3])

[hasan s]

thank you very very much prof. walter for your reply