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Mischa Kim
on 27 Feb 2014

Edited: MathWorks Support Team
on 16 Mar 2021 at 18:56

Benjamin, add

hold on

plot(x_pos,y_pos,'r*')

to your code. (x_pos,y_pos) is the data point that needs to be marked. So if you have

x = 0:0.1:pi;

y = sin(x);

you could use

plot(x,y)

hold on

plot(x(10),y(10),'r*') % marking the 10th data point of x and y

Alternatively, starting in R2016b, you can specify the MarkerIndices property to plot a line with markers at specific data points. For example, plot a line with a marker at the 10th data point.

x = 0:0.1:pi;

y = sin(x);

p = plot(x,y,'o-','MarkerIndices',10)

You can also specify marker properties, such as the face color and edge color.

p = plot(x,y,'o-','MarkerFaceColor','red','MarkerEdgeColor','red','MarkerIndices',10)

Walter Roberson
on 4 Jan 2021

Could you expand on what you mean about plotting points with decimal points? For example are you trying to do

set(h, 'XData', x(20.3), 'YData', y(20.3)); %mark 20.3th point instead.

Greg
on 6 Dec 2017

Edited: Greg
on 6 Dec 2017

With 7k views in a month, I'm surprised this hasn't been updated.

Starting in R2016b, there is a MarkerIndices property. Instead of the other answer's suggested:

plot(x,y);

hold on;

plot(x(10),y(10),'r*');

Now simply use:

h = plot(x,y,'MarkerIndices',10);

Move the marker(s) around at any time if you've stored the handle h:

h.MarkerIndices = 5:5:length(x);

MathWorks Support Team
on 27 Nov 2018

In addition, you can specify the ‘o-‘ line style, which creates a solid line and markers. You can also specify marker properties, such as the face color and edge color.

x = linspace(0,pi,30);

y = sin(x);

p = plot(x,y,'o-','MarkerFaceColor','red','MarkerEdgeColor','red','MarkerIndices',10)

navi g
on 9 Jan 2017

hello, is this marking in plot is possible without writing code, and putting mark in plot in figure editor,

and for sinosoidal curve i have only x data, i dont have y data, but i need to mark on curve, means that i will give x value, based on x value it should place on curve exactly on sinosoidal curve,

Walter Roberson
on 9 Jan 2017

For R2014b or later (I would have to check about earlier; I see some references in 2012 time frame) you can use data brushing. Click on the paintbrush in the figure and then you can click on a point to mark it.

For marking a particular location given only the x, then

x_to_mark = SomeSpecificXValue;

all_lines = findobj(gca, 'type', 'line');

number_of_marks = 0;

where_to_mark = [];

for K = 1 : length(all_lines)

this_line = all_lines(K);

this_xdata = get(this_line, 'XData');

if x_to_mark < min(this_xdata) | x_to_mark > max(this_xdata)

continue; %the line does not span that x

end

x_diff = diff(this_xdata);

if isempty(x_diff)

fprintf('skipping line #%d that is single point\n', K);

elseif all(x_diff > 0) | all(x_diff < 0)

%it is monotonic, safe to do interpolation

this_ydata = get(this_line, 'YData');

y_to_mark = interp1(this_xdata, this_ydata, x_to_mark);

number_of_marks = number_of_marks + 1;

where_to_mark(number_of_marks,:) = [x_to_mark, y_to_mark];

else

fprintf('skipping line #%d with unsorted x data\n', K);

end

end

if number_of_marks == 0

fprintf('That x was not found on a line we could handle\n');

else

hold on

plot(where_to_mark(:,1), where_to_mark(:,2), 'r*');

end

This is probably a lot longer than you were expecting. You did not happen to provide information that we might potentially have used to make it shorter. For example if you know there is only exactly one line, and that the x were sorted when you plotted, and that the x value to mark is definitely in range, then the code could be made much shorter.

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