How to set a marker at a desired location on a plot

Hi,I'm trying to set a marker at integer values of x.I've used index method(x(3)) but couldn't do it.Because I used linspace function.How do I mark my graph when x is equal to an integer number?Thanks.

x=linspace(-4,4);
y=x.*exp(-x.^2);
plot(x,y)
end

Answer 1

[Star Strider]

The easiest way is to define a second vector with integer values, since by inspection only the endpoints of ‘x’ are integers:

x = linspace(-4,4);
xi = min(x) : max(x);                           % Integer ‘x’ Vector
y = x.*exp(-x.^2);
yi = xi.*exp(-xi.^2);
plot(x,y)
hold on
plot(xi, yi, 'rp', 'MarkerFaceColor','g')
hold off
grid

Answer 2

[John BG]

use a vector index, let it be k, instead of the x reference of the plot.

1.

plot and add a marker

x=linspace(-4,4);
y=x.*exp(-x.^2);
plot(x,y)
hold on
p = plot(x(1),y(1),'o','MarkerFaceColor','red');

2.

now you can simply place the marker on one of the plotted points of y by varying k between 1 and numel(y), for instance:

k=20;
p.XData = x(k);
p.YData = y(k);

or

hold on;
p = plot(x(k),y(k),'o','MarkerFaceColor','red');
hold off;

the figure window also has a marker called Data Cursor.

if you find these lines useful would you please mark my answer as Accepted Answer?

To any other reader, if you find this answer of any help, please click on the thumbs-up vote link,

thanks in advance for time and attention

John BG

<mailto:[e-mail] [e-mail]>

Answer 3

[absomnia48]

Hey,another question here.I'm supposed to find the minimum and maximum value on the graph and draw a line until the axis.I have to do it with 'fminbnd' function.I'm writing this;

    [-0.6869,-0.4285]=fminbnd(@xx.*exp(-x.^2),-0.6,0.6)
%or this one 
    fminbnd(x.*exp(-x.^2),-4,4)

but didn't work.Matlab tells me this 'Error: An array for multiple LHS assignment cannot contain expressions.'Thank you for the help

[Star Strider]

You are almost there with the ‘%or this one’ version. You only need to add a function handle, here that would be ‘@(x)’:

fx = @(x) x.*exp(-x.^2);
Ymin = fx(fminbnd(fx, -4, 4))
Ymax = fx(fminbnd(@(x) -fx(x), -4, 4))

Ymin =
  -428.8819e-003

Ymax =
   428.8819e-003

Note that to get the maximum, take the minimum of the negative of the funciton.

[John BG]

Start Strider, Y maxmin are

Ymax=0.42
Ymin=-0.42

while

Xmin=-0.707 
Xmax=0.707

because

x=[-4:.00001:4]; y=x.*exp(-x.^2);
       min(y)
      =
        -0.428881942471466
       max(y)
      ans =
         0.428881942471466
       find(y==min(y))
       =
            329290
       x(find(y==min(y)))
       =
        -0.707110000000000