# How to find the error between two plots and plot the error in same diagram

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Abdul Sajeed Mohammed
on 15 Feb 2022

Commented: Robert U
on 24 Feb 2022

I need to plot error between two plots Ground_truth and Estimated_Long_Lat

Sharing my code here

figure;

Estimated_long = 180 / pi * lon;

Estimated_Lat = 180 / pi * lat;

plot(180 / pi * lon, 180 / pi * lat,'x','Linewidth',0.5);

hold on

Ground_Truth = xlsread('27');

G_Long = Ground_Truth(:,1);

G_Lat = Ground_Truth(:,2);

plot(G_Long,G_Lat,'-x','Linewidth',2)

hold on

hold off

ylabel('Latitude, [deg]','FontSize', 13);

xlabel('Longitude, [deg]','FontSize', 13);

title('Trajectory of vehicle with position close to Lane level','FontSize', 15)

legend('Estimated trajectory', 'Centre nodes of True trajectory','best')

Thanks

### Accepted Answer

Robert U
on 15 Feb 2022

Hi Abdul Sajeed Mohammed,

here some example that is close to what you do:

% example data params (circular trajectory)

R = 1000;

phi = 0:360;

% uniformly distributed noise (signed)

noise = 100 .* (rand(1,length(phi)) - 0.5);

% generate example date

Estimated_long = R .* sind(phi) + noise;

Estimated_Lat = R .* cosd(phi) + circshift(noise,floor(length(phi)/2));

% generate ground truth data

Ground_Truth = R .* [sind(phi); cosd(phi)];

G_Long = Ground_Truth(1,:);

G_Lat = Ground_Truth(2,:);

% Choose whatever error norm is applicable

totalErr = sqrt((Estimated_Lat - G_Lat).^2 + (Estimated_long - G_Long).^2);

% create figure with two subplots

fh = figure;

fh.OuterPosition = fh.OuterPosition .* [0.5 0.5 2 2];

sh{1} = subplot(1,2,1,'Parent',fh);

sh{2} = subplot(1,2,2,'Parent',fh);

hold(sh{1},'on')

axis(sh{1},'equal')

% plot measured and ground truth data into first subplot

plot(sh{1},Estimated_long, Estimated_Lat,'x','Linewidth',0.5);

plot(sh{1},G_Long,G_Lat,'-x','Linewidth',2)

ylabel(sh{1},'x, [m]','FontSize', 13);

xlabel(sh{1},'y, [m]','FontSize', 13);

title(sh{1},'Trajectory of vehicle with position close to Lane level','FontSize', 15)

legend(sh{1},'Estimated trajectory', 'Centre nodes of True trajectory')

% plot total error in second subplot

plot(sh{2},phi,totalErr,'.','MarkerSize',12);

xlabel(sh{2},'phi, [deg]','FontSize', 13);

ylabel(sh{2},'total error, [m]','FontSize', 13);

title(sh{2},'Total error of vehicle','FontSize', 15)

Concerning error norms, have a look here:

- https://en.wikipedia.org/wiki/Norm_(mathematics)
- http://www.math.pitt.edu/~sussmanm/2071Spring09/lab05/index.html

Kind regards,

Robert

##### 5 Comments

Robert U
on 24 Feb 2022

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