Draw plot and display results Matlab - matlab

Question

I'm working on bisection method which I wrote by myself. The following code works fine - it displays correct results(Tested on x^2-25) and it gave correct results. But that's not all what I wanted to realize.I need draw a plot displaying all correct results on it.
As I told - I took expression
x^2-25
, and results are
5 and -5
Now, I need to draw parabola and display results.
My Code
function [] = bisectionWindow()
clc;
f = #(x) x^2-25; % specified function
a=5;
b=6;
e=0.0001;
syms x;
% Main loop
while abs(b-a)>e
c=(b+a)/2;
if sign(f(c)) == sign(f(a))
a=c;
else
b=c;
end
end
disp(['Answer x='])
solve(f(x))
%note: ans displays because of 'sign' operator presence
My Attempt to draw plot
function [] = checkWin(a,b,x)
%draws plot
Limits = [a b];
len = b-a;
for i=1:len
x = X(i);
y=x^2-25;
%y=0.5*x^3-2*x^2+1;
figure(1),clf,hold on
fplot('x^2-25',Limits),grid
plot(x,y,'o')
end
end
UPD: To clear some things up
I understand how to draw a plot. My objective is:
Show the plot
Show results as o's on it
The problem is - this should be unique code (as for example i took parabola, but let's take another function which has only one result) and it should execute things metioned above. So basically this is why i'm working on.
There's 2 options:
Modify existing code - which i dunno how
Rewrite - no ideas how.
I'm stuck for a long time I guess.
Thanks for Advices.

Answer 1

I don't get why you need the loop in your code. The following script works fine and gives the same result as yours:
f = #(x) x^2-25; % specified function
disp(['Answer x='])
disp(solve(f(x)))
You can plot your function by typing ezplot(f):
Typing ezplot(f,[-5,5]) would plot function with x between -5 and 5
If you want to use plot function, you need to rewrite your function as:
f = #(x) x.^2-25
This is because ^2 operation is regarded as multiplication of matrix by itself that is inapplicable to vectors, whereas .^2 is squaring of each matrix element.
Then, you need to create two vectors with x and y data and use plot function:
x = -10:0.1:10;
y = f(x);
plot(x,y), grid on
where grid on provides your plot with gridlines. There are many other plot options that you can use to customize your graph. You can find them here
UPD. Modified code with comments:
f = #(x) x.^2-25; %//specified function
disp(['Answer x='])
q = solve(f); %//-5 and 5 would be in one vector
disp(q) %//display -5 and 5
h = ezplot(f,[-10,10]); %//plot f(x) from -10 to 10
grid on; %//add grid to plot
set(h,'LineWidth',3); %//set line width to 3px
hold on;%//prevent the current graph from being replaced
plot(q,f(q),'ro','MarkerSize',10,'LineWidth',3)
%//plot two O-s at -5 and 5. Also, make O-s 10px in width and 3px thick
hold off;
This yields: