How to set a scale in a figure (similiar to Google Maps)

Hi all,

I have the following set of data, time versus Intensity. When I plot them want to draw a scale that changes accordingly with the zoom. I want to start with a default scale of 10 second. At the moment I zoom-in the figure, I want the scale to be shorter (something like Google Maps), for example, from 10 seconds to 1 second, and 0.05 second. Also, I want the scale be fixed to the figure. Therefore, I can pan the data and match the scale to the spikes you see in the figure. I have been using a line to check the baseline drift. The line is fixed to the figure, so I can pan the data and match the line to the beggining of the spike. I want to do the same with the scale (again, something similar to Google Mpas scale).

[Jose Rego Terol]

http://www.mathworks.com/matlabcentral/fileexchange/25799-scale-bar-for-2d-axes

I cannot set this scalebar in my code

f1=figure(1);
           
           
set(f1,'units','normalized','position',[0 0 1 1],'NumberTitle','on','ToolBar', 'None');
f1.WindowState = 'maximized';
hold on;box on; grid on; 
plot(x,y,'b');%axis tight;
ylabel('Amplitud (pA)');
xlabel({'Time (s)'; ['foot-Spike:' num2str(fs) '     Flicker:'  num2str(fl)...
    '     Kiss and Run:'  num2str(KnR) '     Null:'  num2str(null)]})

    axis([x(1) x(length(x)) min(abs(y)) max(y)]); % Update plot
title(['Select two points around a ROI            Event(s) so far:  ' num2str(mNum)]);
ylim([-100 200]);

Answer 1

[Joseph Cheng]

I don't understand what you're doing with that line to check baseline. I'll continue to read that however here is a quick scale bar that i'll let you adjust to stay locked to one of your scale bar sizes. This should get you going and you can adjust the scale plot color, shape etc, to get it how you'd like to see it. Especially adjusting the position within the frame

 function Matlabanswer()
%gen dummy data
    t=0:.001:10;
    intensity = rand(size(t)).^2.*rand(size(t)).^10+rand(size(t)).^100;
    hfig = figure(1);clf
    hax(1) = axes(hfig);
    plot(hax(1),t,intensity),xlabel('time'),ylabel('instensity');
    ylim([0 20])
    hax(2) = axes(hfig); %create the floating box where the scaler bar will be located
        scalePos = [hax(1).Position(1)...
                    hax(1).Position(2)+hax(1).Position(4)-.1...
                    .1*hax(1).Position(3)...
                    .1*hax(1).Position(4)]; %designate upper left corner 
                                            %and scale secondary axes to be
                                            %1/10 the size
    hax(2).Position = scalePos; %scale the 2nd axes to the first.
    
    plot(hax(2),t,zeros(size(t))) %plot data
    xlim(hax(2),hax(1).XLim) %plot line the same length as data but in the 1/10 axes
   set(hax(2),'XColor', 'none','YColor','none','color','none') %make scale axes invisible
    
   %here is the section for annotation of what the scale line is
    hanno = annotation('textbox', scalePos-[0 .05 0 0], 'String', ...
            ['scale ' num2str(.1*(diff(hax(1).XLim))) 'x']);
    hanno.LineStyle='none';
    
    %initiate the function for what happens when zooming
    hzoom = zoom(hfig);
    set(hzoom,'ActionPostCallback',{@myzoomfunction,hax,hanno});

function myzoomfunction(obj,event,AX,AnnoText)
    xlim(AX(2),AX(1).XLim); %update the scale axes to match up with zoomed data
    AnnoText.String=['scale ' num2str(.1*(diff(AX(1).XLim))) 'x']; %update the scale annotation

[Jose Rego Terol]

Hi Joseph,

This is what I was looking for with some variations. I saw this code (https://cn.mathworks.com/matlabcentral/fileexchange/59018-chenxinfeng4-scalebar), but the scalebar is not steady as yours. When I pan the plot, the scalebar moves as well. Yours, in contrast is steady. May you help me? Do you know how can I keep it steady?

About the line: If I draw a line, I can detect easily when the signal rises above the baseline. When I pan the plot, the line is steady to the window. Therefore, I do not need to move the line to check the signal in the following spikes. So I wanted to transform this line into a scalebar. I check the signal baseline while I can measure the time frame. Do you understand?

[Jose Rego Terol]

Hi again Joseph,

Thank you very much for this code. It is almost what I want. There is only few thing I wuold like to comment.

I finished implementing your code. It looks good but there are three issues that I need your help to solve them.

First, let me show you the figure:

As you can see, there are two different scales for each axis. I don't know how to remove the additional axes that your code have.

The second issue is the scale. I would like to represent the scale as a time reference. It means that the default bar length is 10 seconds, for example. In this sense, I would prefer the code from Cheng (https://de.mathworks.com/matlabcentral/fileexchange/59018-chenxinfeng4-scalebar).

Last but not least, the scale is steady to the window. This property is perfect because I can pan the plot, and the scale is attached to the figure. However, I would like to place it in the middle of the figure. Even though the code is full of comments, I tried to find the part of the code for this purpose, but I cannot find it. Where can I set the position fo the scale?

Thanks again for your time. I really appreciate the effort you did for this code.

[Joseph Cheng]

How about this. sorry i was busy with my day job.

I simplified it instead of using an additional axis plotted into the window you can use annotations and know how it scales with the plot.

This will lock it to the center of the screen. if you don't want the text to be in that location. Just move the arrow annotation text into a new annotation text box in the location where you want it to be. As these annotation is locked to the figure it will not change when panned around. I only did the X axis however if you read up on the annotation() function you can just as easily make it for a Y scale bar too

function Matlabanswer()
%gen dummy data
    t=0:.001:100;
    intensity = rand(size(t)).^2.*rand(size(t)).^10+rand(size(t)).^100;
    hfig = figure(1);clf
    hax = axes(hfig);
    plot(hax,t,intensity),xlabel('time'),ylabel('instensity');
    grid minor
   
   %here is the section for annotation of what the scale line is
    initScaleLengthsec = 10;%in seconds
    initScaleLengthNorm = initScaleLengthsec/diff(hax.XLim); % ratio of the scale length
        %against the span of the plot limits as we'll be dealing with normalized
        % % to the figure window
    %generate the X and Y locations here.  since these are in normalized space of the figure
    %example here is scalePosX start and stop of the arrow is half the plot window size
    % and half the plot window size + the ratio of the window size.
    %this is then offset by Position(1) since the position(1) is the lower left corner of the 
    %plot in relation to the window. 
    %read up on the position attribute since this is the best i can describe right now.
    %position attribute [lowerleftX lowerleftY width height];
    scalePosX = [hax(1).Position(3)*1/2,...
                hax(1).Position(3)*1/2+initScaleLengthNorm*hax(1).Position(3)]+...
                hax(1).Position(1);
    %set Y position of the arrow as half way up the height (position(4)) and offset by 
    %position of the plot axes.
    scalePosY = [hax(1).Position(2)+hax(1).Position(4)/2,...
                hax(1).Position(2)+hax(1).Position(4)/2];            
    
    %generate text arrow.
    hanno = annotation('textarrow',scalePosX,scalePosY, 'String', ...
            [num2str(initScaleLengthsec) 'seconds']);    
    %initiate the function for what happens when zooming
    hzoom = zoom(hfig);
    set(hzoom,'ActionPostCallback',{@myzoomfunction,hax,hanno});
    %edit these callbacks should be in there as you can zoom with scroll mouse
    %and double click which will reset the view but not trigger the update in scale
    hfig.WindowButtonUpFcn={@myzoomfunction,hax,hanno};
    hfig.WindowScrollWheelFcn={@myzoomfunction,hax,hanno};

function myzoomfunction(obj,event,AX,AnnoText)
    %find the span of the plot
    plotSpan = diff(AX.XLim);
    %my attempt to set the limits of when to update annotation.
    switch true
      case plotSpan>50
        span=10;
    case plotSpan<=50 && plotSpan>25 
        span=5;
    case plotSpan<=25 && plotSpan>10
        span=2;
    case plotSpan<=10 && plotSpan>2
        span=.5;        
    case plotSpan<=2 && plotSpan>.1
        span=0.05;
    otherwise
        span=0.01;
    end
    %again find the new ratio of width of plot to desired scale span
    ScaleLengthNorm = span/diff(AX.XLim);
    
    %generate again how long the arrow is
    scalePosX = [AX(1).Position(3)*1/2,...
                AX(1).Position(3)*1/2+ScaleLengthNorm*AX(1).Position(3)]+...
                AX(1).Position(1);
    scalePosY = [AX(1).Position(2)+AX(1).Position(4)/2,...
                AX(1).Position(2)+AX(1).Position(4)/2];            
    
    %update the annotation's X start stop
    AnnoText.X=scalePosX;
    %update the annotation's Y start stop
    AnnoText.Y=scalePosY;
    %update the text to new span.
    AnnoText.String=[num2str(span) 'seconds'];    

[Jose Rego Terol]

I am so sorry Joseph. I could not respond until now.

Your code is working good. Thi is what I wanted to have. Thanks a lot.