Hello! How can i delete a line from my figure?

Hello! I have an image from which i would like to delete a line. How can i do that? When i use the delete() function it does not work. There is no error mentioned nor is the image changing.

Please help!

Answer 1

[Image Analyst]

This should work

hLine = line(x, y, 'Color', 'r', 'LineWidth', 2);
% Now delete it.
delete(hLine);

[Stany Stone]

But if my line results from a plot? Will it change anything?

[Walter Roberson]

You need to find the handle of the object you wish to delete (or set its visibility to off) . findobj() can help for that.

[Stany Stone]

Ook! Thank you for your answears! So, say i have the plot and then i add findobj(). What do i put inside those parantheses? The structure that i actually have în the plot phase? P

[Walter Roberson]

If there is only one line in the plot

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

After which you can delete(hLine) or set(hLine, 'visible', 'off')

If there are multiple lines in the plot, then what (if anything) do you know that is different about the line? For example is it the only line that uses dashes to draw? Is it the only cyan line?

[Image Analyst]

If there are multiple lines, Walter's code will delete all of them. If you don't want to delete all of them, but only want one particular line from a set of multiple lines that are on the graph, then it's best if you just store the handle of that particular one right when it's created, and then pass that one particular handle into delete().

[Stany Stone]

Thank you! But if my code is like this:

                     xKnown - halfLineLength*cos(perTheta)];
yPerKnown = [yKnown + halfLineLength*

sin(perTheta), ...
                   yKnown - halfLineLength*sin(perTheta)];
% calculate the ends points of another newL based on the Unknown points of oldL
xPerUnknown = [xUnknown + halfLineLength*cos(perTheta), ...
                      xUnknown - halfLineLength*cos(perTheta)];
yPerUnknown = [yUnknown + halfLineLength*sin(perTheta), ...
                      yUnknown - halfLineLength*sin(perTheta)];
% draw these two newL
plot([xPerKnown(1), xPerKnown(2)], [yPerKnown(1), yPerKnown(2)], 'o-', ...
  'Color', darkGreen, 'MarkerSize', 24, 'LineWidth', 3);
plot([xPerUnknown(1), xPerUnknown(2)], [yPerUnknown(1), yPerUnknown(2)], 'o-', ...
  'Color', darkGreen, 'MarkerSize', 24, 'LineWidth', 3)

Then it means that i have to use the hLine=findobj() immediately after the plot of the line i want to delete? And, in this case, the thing that makes the line unique isn't about the width or the color. What should i put in the parantheses to differentiate the one i want?

[Image Analyst]

You can save the result of plot(), then call delete() on those handles when you need to or want to:

% draw these two newL
hPlot1 = plot([xPerKnown(1), xPerKnown(2)], [yPerKnown(1), yPerKnown(2)], 'o-', ...
  'Color', darkGreen, 'MarkerSize', 24, 'LineWidth', 3);
hPlot2 = plot([xPerUnknown(1), xPerUnknown(2)], [yPerUnknown(1), yPerUnknown(2)], 'o-', ...
  'Color', darkGreen, 'MarkerSize', 24, 'LineWidth', 3)
% More code.... then later, when you want to delete them....
delete(hPlot1); % Delete line created from plot().
delete(hPlot2); % Delete line created from plot().

[Walter Roberson]

Yes, recording the handle will always be a better solution rather than findobj when it can be done. Sometimes though you are wanting to delete a line from a plot created by code you do not have control of, or from a stored fig that you cannot change the generation code for, and in those cases you would use findobj or findall

[Stany Stone]

Thnak you so much for your answears!