Annotating an Arrow with in a plot.

I am trying to use the annotation function to show an arrow on my plot like ar = annotation('arrow'..) I know the location where I want the arrow to start the x and y coordinates in my data units. However, the documentation says I can only specify in normalized units which are between 0 and 1 for any figure. But this will not work for me. So what is a work around so that I can put the arrow exactly at a point specified by userdata.

[Pappu Murthy]

When I first create the figure it looks like this: picture file one.png

I click on plot tools icon it then fills my screen and i see it full size but my arrows are all badly placed now.

Answer 1

[Jan]

See: FEX: Transform axes units for annotation objects

See also: https://www.mathworks.com/matlabcentral/answers/346297-how-to-draw-an-arrow-using-non-normalized-coordinates

Searching in this forum and in the FileExchange is a good idea.

[Pappu Murthy]

I tried the FEX function it works fine for me. But again When I change the plots to fullscreen mode with plottools on the arrows get displaced badly.

Answer 2

[Pappu Murthy]

the link helped me solve the problem partially. When I click on maximize the window with plot tools, all the arrow positions are screwed up. Or if I place the arrows after I adjust the figure to fit the window and click on plot tools, then the arrows are placed correctly. However, I have no control to make the figure full screen and with plot tools enabled without manually clicking the options. How do i overcome this?

[Walter Roberson]

set(gcf, 'units', 'normal', 'Position', [0 0 1 1])

[Pappu Murthy]

I tried this it seems to work the figure occupied the full screen and arrows looked right. But the moment I click on the "plot tools" button the picture becomes somewhat smaller due to the placement of all the plot tool components. While 99% of the figure is still okay, the arrows I placed are no longer properly positioned. Why? May be it is a Matlab bug. So problem is the entire figure is not gracefully scalable.

[Pappu Murthy]

Some nothing seems to work ok with my specific case. If I create a sample case it seems to work. So what I finally tried after searching through Matlab helpfile is to include a line "plottools('on') before I create my 'arrows' and it worked like charm. So I am going to close this question. Thanks for all the help provided. They did solve most of the problem if not 100%.

Answer 3

[Nirjhar Kumar]

Adapted marcus yoder code at https://in.mathworks.com/matlabcentral/answers/346297-how-to-draw-an-arrow-using-non-normalized-coordinates .

open a figure and Just pass the position of x data's to the below function

function obj = dataArrow2(xpos)
%This function will draw an arrow on the plot for the specified x data position .
%Eg:
% plot(0:0.001:10,sin(0:0.001:10))
% dataArrow2([3000 6000 9000])

handles=findall(0,'type','figure');
for fig_cnt= 1:1:length(handles)
    figure(handles(fig_cnt,1))
    ax=handles(fig_cnt,1);   
%     hLeg=findobj(handles(fig_cnt,1),'type','legend');
%     set(hLeg,'visible','off')
    
    axObjs=findobj(handles(1,1),'type','Axes');%axObjs = ax.Children;
    dataObjs = axObjs.Children;
    
    oldunits = get(axObjs, 'Units');
    set(axObjs, 'Units', 'Inches');
    axpos = axObjs.Position
    set(ax, 'Units', oldunits);
    
    oldunits = get(handles, 'Units');
    set(handles, 'Units', 'Inches');
    figpos= handles.Position
    set(handles, 'Units', oldunits);
    
%     set(hLeg,'visible','off')
    %get axes drawing area in data units
    ax_xlim = ax.CurrentAxes.XLim;
    ax_ylim = ax.CurrentAxes.YLim;
    ax_per_xdata = axpos(3) ./ diff(ax_xlim);
    ax_per_ydata = axpos(4) ./ diff(ax_ylim);

    for i=1:1:length(dataObjs)
        Xdata = dataObjs(i).XData;
        Ydata = dataObjs(i).YData;
        %these are figure-relative
        for j=1:1:length(xpos)
            Xpixels = (Xdata([xpos(j) xpos(j)+1]) - ax_xlim(1)).* ax_per_xdata+axpos(1);
                 %if set(gca,'xdir','reverse') is used
                 %Xpixels = -(Xdata([pos pos+1]) - ax_xlim(1)).* ax_per_xdata+axpos(3)+axpos(1);
            Ypixels = (Ydata([xpos(j) xpos(j)+1]) - ax_ylim(1)).* ax_per_ydata+axpos(2);
                  %if set(gca,'ydir','reverse') is used
                  %Ypixels = -(Ydata([pos pos+1]) - ax_ylim(1)).* ax_per_ydata+axpos(2)+axpos(4);
            annotation('arrow', Xpixels/figpos(3), Ypixels/figpos(4));
        end;
        obj = 1;
    end
end;