crosshairs or just vertical line across linked axis plots

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What I have are plots that are linked by the linkaxes() function. I would like to have a vertical line that spans all of the plots so that I can compare the peaks and valleys interactively between plots.

Accepted Answer

Jiro Doke
Jiro Doke on 22 Feb 2011
This may get you started:
function vertical_cursors
set(gcf, ...
'WindowButtonDownFcn', @clickFcn, ...
'WindowButtonUpFcn', @unclickFcn);
% Set up cursor text
allLines = findobj(gcf, 'type', 'line');
hText = nan(1, length(allLines));
for id = 1:length(allLines)
hText(id) = text(NaN, NaN, '', ...
'Parent', get(allLines(id), 'Parent'), ...
'BackgroundColor', 'yellow', ...
'Color', get(allLines(id), 'Color'));
end
% Set up cursor lines
allAxes = findobj(gcf, 'Type', 'axes');
hCur = nan(1, length(allAxes));
for id = 1:length(allAxes)
hCur(id) = line([NaN NaN], ylim(allAxes(id)), ...
'Color', 'black', 'Parent', allAxes(id));
end
function clickFcn(varargin)
% Initiate cursor if clicked anywhere but the figure
if strcmpi(get(gco, 'type'), 'figure')
set(hCur, 'XData', [NaN NaN]); % <-- EDIT
set(hText, 'Position', [NaN NaN]); % <-- EDIT
else
set(gcf, 'WindowButtonMotionFcn', @dragFcn)
dragFcn()
end
end
function dragFcn(varargin)
% Get mouse location
pt = get(gca, 'CurrentPoint');
% Update cursor line position
set(hCur, 'XData', [pt(1), pt(1)]);
% Update cursor text
for idx = 1:length(allLines)
xdata = get(allLines(idx), 'XData');
ydata = get(allLines(idx), 'YData');
if pt(1) >= xdata(1) && pt(1) <= xdata(end)
y = interp1(xdata, ydata, pt(1));
set(hText(idx), 'Position', [pt(1), y], ...
'String', sprintf('(%0.2f, %0.2f)', pt(1), y));
else
set(hText(idx), 'Position', [NaN NaN]);
end
end
end
function unclickFcn(varargin)
set(gcf, 'WindowButtonMotionFcn', '');
end
end
Save the above function. Here's an example of how to use it:
subplot(221);
plot(rand(10,1));
subplot(222);
plot(rand(10,2));
subplot(223);
plot([rand(10,1), rand(10,1)+1]);
subplot(224);
plot(rand(10,1));
vertical_cursors;
EDIT: As a response to a request, I added the ability to make the cursor disappear when clicking outside the axes. See the two lines of code with the comment "<-- EDIT".
  10 Comments
Ferd
Ferd on 4 Apr 2019
Hi,
I tried the example given and it works without issues. Then on another figure with 4 subplots that I've linked their x-axes, I've come across this error below,
Is there a way to get around this error message?
Error using griddedInterpolant
The grid vectors must contain unique points.
Error in interp1 (line 149)
F = griddedInterpolant(X,V,method);
Error in vertical_cursors/dragFcn (line 41)
y = interp1(xdata, ydata, pt(1));
Error in vertical_cursors/clickFcn (line 28)
dragFcn()
Error while evaluating Figure WindowButtonDownFcn.
Error using griddedInterpolant
The grid vectors must contain unique points.
Error in interp1 (line 149)
F = griddedInterpolant(X,V,method);
Error in vertical_cursors/dragFcn (line 41)
y = interp1(xdata, ydata, pt(1));
Error in vertical_cursors/clickFcn (line 28)
dragFcn()
Error while evaluating Figure WindowButtonDownFcn.
Error using griddedInterpolant
The grid vectors must contain unique points.
Error in interp1 (line 149)
F = griddedInterpolant(X,V,method);
Error in vertical_cursors/dragFcn (line 41)
y = interp1(xdata, ydata, pt(1));
Error while evaluating Figure WindowButtonMotionFcn.
Error using griddedInterpolant
The grid vectors must contain unique points.
Error in interp1 (line 149)
F = griddedInterpolant(X,V,method);
Error in vertical_cursors/dragFcn (line 41)
y = interp1(xdata, ydata, pt(1));
Error while evaluating Figure WindowButtonMotionFcn.
Error using griddedInterpolant
The grid vectors must contain unique points.
Error in interp1 (line 149)
F = griddedInterpolant(X,V,method);
Error in vertical_cursors/dragFcn (line 41)
y = interp1(xdata, ydata, pt(1));
Error while evaluating Figure WindowButtonMotionFcn.
Error using griddedInterpolant
The grid vectors must contain unique points.
Error in interp1 (line 149)
F = griddedInterpolant(X,V,method);
Error in vertical_cursors/dragFcn (line 41)
y = interp1(xdata, ydata, pt(1));
Error while evaluating Figure WindowButtonMotionFcn.
Error using griddedInterpolant
The grid vectors must contain unique points.
Error in interp1 (line 149)
F = griddedInterpolant(X,V,method);
Error in vertical_cursors/dragFcn (line 41)
y = interp1(xdata, ydata, pt(1));
Error while evaluating Figure WindowButtonMotionFcn.
Error using griddedInterpolant
The grid vectors must contain unique points.
Error in interp1 (line 149)
F = griddedInterpolant(X,V,method);
Error in vertical_cursors/dragFcn (line 41)
y = interp1(xdata, ydata, pt(1));
Error while evaluating Figure WindowButtonMotionFcn.
Error using griddedInterpolant
The grid vectors must contain unique points.
Error in interp1 (line 149)
F = griddedInterpolant(X,V,method);
Error in vertical_cursors/dragFcn (line 41)
y = interp1(xdata, ydata, pt(1));
Error while evaluating Figure WindowButtonMotionFcn.
Matthias Luh
Matthias Luh on 19 Mar 2022
Edited: Matthias Luh on 19 Mar 2022
Thank you very much for the code!
I extended it for datetime x-axis compatibility:
function vertical_cursors
set(gcf, ...
'WindowButtonDownFcn', @clickFcn, ...
'WindowButtonUpFcn', @unclickFcn);
% Set up cursor text
allLines = findobj(gcf, 'type', 'line');
hText = nan(1, length(allLines));
for id = 1:length(allLines)
hText(id) = text(NaN, NaN, '', ...
'Parent', get(allLines(id), 'Parent'), ...
'BackgroundColor', 'yellow', ...
'Color', get(allLines(id), 'Color'));
end
% Set up cursor lines
allAxes = findobj(gcf, 'Type', 'axes');
hCur = nan(1, length(allAxes));
for id = 1:length(allAxes)
if isa(xlim(allAxes(id)), 'datetime') == 1
x_lims = xlim(allAxes(id));
%default_time = x_lims(1) + diff(x_lims) / 2; % Option A) use mid
default_time = NaT('TimeZone',x_lims(1).TimeZone); % Option B) don't display at start
nan_data = [default_time default_time];
else
nan_data = [NaN NaN];
end
hCur(id) = line(nan_data, ylim(allAxes(id)), ...
'Color', 'black', 'Parent', allAxes(id));
end
function clickFcn(varargin)
% Initiate cursor if clicked anywhere but the figure
if strcmpi(get(gco, 'type'), 'figure')
if isa(xlim(gca), 'datetime') == 1
x_lims = xlim(gca);
nan_time = NaT('TimeZone',x_lims(1).TimeZone);
nan_data = [nan_time nan_time];
else
nan_data = [NaN NaN];
end
set(hCur, 'XData', nan_data);
set(hText, 'Position', [NaN NaN]);
else
set(gcf, 'WindowButtonMotionFcn', @dragFcn)
dragFcn()
end
end
function dragFcn(varargin)
% Get mouse location
pt = get(gca, 'CurrentPoint');
% Update cursor line position
set(hCur, 'XData', [pt(1), pt(1)]);
% Update cursor text
for idx = 1:length(allLines)
xdata = get(allLines(idx), 'XData');
ydata = get(allLines(idx), 'YData');
if isa(xlim(gca), 'datetime') == 1
if pt(1) >= get_date_xpos(xdata(1)) && pt(1) <= get_date_xpos(xdata(end))
x_lims = xlim(gca);
x = pt(1) + x_lims(1);
data_index = dsearchn(get_date_xpos(xdata'),get_date_xpos(x));
x_nearest = xdata(data_index);
y_nearest = ydata(data_index);
set(hText(idx), 'Position', [pt(1), y_nearest], ...
'String', sprintf('(%s, %0.2f)', datestr(x_nearest), y_nearest));
% y = interp1(get_date_xpos(xdata), ydata, pt(1));
% set(hText(idx), 'Position', [pt(1), y], ...
% 'String', sprintf('(%s, %0.2f)', datestr(pt(1)), y));
else
set(hText(idx), 'Position', [NaN NaN]);
end
else
if pt(1) >= xdata(1) && pt(1) <= xdata(end)
y = interp1(xdata, ydata, pt(1));
set(hText(idx), 'Position', [pt(1), y], ...
'String', sprintf('(%0.2f, %0.2f)', pt(1), y));
else
set(hText(idx), 'Position', [NaN NaN]);
end
end
end
end
function unclickFcn(varargin)
set(gcf, 'WindowButtonMotionFcn', '');
end
function xpos = get_date_xpos(x_value)
ax1 = gca;
% dx_days = diff(ax1.XLim)/24;
x_min = ax1.XLim(1);
xpos = datenum(x_value - x_min);
end
end

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More Answers (3)

Jiro Doke
Jiro Doke on 22 Feb 2011
Does the answers from this question help?
  2 Comments
Mark Dragovan
Mark Dragovan on 22 Feb 2011
It's not exactly what I had in mind, but is close. I would be happy with a vertical line that I can control with the mouse position that spans multiple plots.
Thanks for the reference to that question, it will get me started.

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Patrick Kalita
Patrick Kalita on 22 Feb 2011
How about just using the Pointer property on the figure?
f = figure;
subplot(2,1,1)
plot(rand(5))
subplot(2,1,2);
plot(magic(5))
set(f, 'Pointer', 'fullcrosshair')
  4 Comments
Walter Roberson
Walter Roberson on 22 Feb 2011
I see what you mean, Patrick. On the other hand, it would cover the entire figure rather than just the plots.
Jiro Doke
Jiro Doke on 22 Feb 2011
It seems that this solution is the easiest and cleanest when the axes are stacked vertically. I'm not entirely sure what the OP meant when he said "compare the peaks and valleys interactively between plots". Is it just visually line things up, or does he want more information like actual numbers.

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claudio
claudio on 26 May 2014
Is it possible to display the values in a window (like in datacursormode, "window inside figure" display style)??

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