Minimum point of Graph

I have plotted a parabola like curve in the rough shape of (y=x^2). How am I able to draw plot a verical line from the minimum of the graph where the gradient is zero to the x axis and have this labbled as (Xminimum). Is it also possible to obtain an x value at which this value occurs on the graph too

Thanks

Answer 1

[Mark Sherstan]

Use the islocalmin function:

x = -5:0.1:5;
y = x.^2;

idx = islocalmin(y);

figure(1)
hold on
plot(x,y)
plot(x(idx),y(idx),'*r')
legend('Curve','Local Min')
hold off

fprintf('Min located at %0.2f\n',x(idx))

[Andrew Kay]

Is it possible to have a vetical line drawn from from the minimum to the x axis? Basically my graph isnt exactly a 'y=x^2' graph and doesnt touch the x axis. I only said that for sy in understaning. Thanksimplicit

[Mark Sherstan]

Use the line function! Here you go :)

x = -5:0.1:5;
y = x.^2 - 5;

idx = islocalmin(y);

figure(1)
hold on
plot(x,y)
plot(x(idx),y(idx),'*r')
line([x(idx) x(idx)],[y(idx) 0])
hold off

fprintf('Min located at %0.2f\n',x(idx))

[Andrew Kay]

Great that works excellent thanks! Is there a way i can chose the colour of that line/ a coloured dashed line?

[Mark Sherstan]

Right now this is a black dashed line. More options can be found towards the bottom of the page here.

line([x(idx) x(idx)],[y(idx) 0],'color','k','LineStyle','--')

[Andrew Kay]

Very Helpful, thanks for your time

Answer 2

[madhan ravi]

syms x
y=x^2
x=solve(diff(y)==0)