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How do I plot error in both the x and y directions as a shaded area?

Asked by Anthony Lapsansky on 2 Sep 2019
Latest activity Answered by Subhadeep Koley on 5 Sep 2019
I am trying to plot a Lift:Drag polar (a common graph in aerodynamics for evaluating wings) which has error in both the x and y directions. I am able to plot the points and the error associated with those points using the 'errorbar' function in Matlab, but I was hoping to shade the area between the errorbars. Currently, my plot looks like this:
Is there a way to shade the area between the four bounds for each point? The typical methods using flipud end up filling the center of the u-shape, which I don't want to do. Currently, my code for the 'errorbar' plot looks like this:
figure()
errorbar(ChFl_means, CvFl_means, -CvFl_sem, CvFl_sem, -ChFl_sem, ChFl_sem, 'Color', 'b','LineWidth', 1); %plot Flexed Data
hold on
errorbar(ChE_means, CvE_means, -CvE_sem, CvE_sem, -ChE_sem, ChE_sem, 'Color', 'r','LineWidth', 1); %plot Extended Data
legend('Flexed Posture', 'Extended Posture')
ylabel('Cv')
xlabel('Ch')

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Anthony Lapsansky added —
I have made a simple version of my data for testing.
figure() %no x error
x = [5 4 3 2 1 0.5 1 2 3 4 5];
y = [0 0.25 0.75 1.5 2 2.5 3 3.5 4.5 4.75 5];
x_err = [0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5];
y_err = [0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5];
hold on
patch([x fliplr(x)], [y+y_err fliplr(y-y_err)],[0.8 0.8 0.8])
errorbar(x,y,-y_err,y_err,-x_err,x_err,'-')
figure() %x error included
x = [5 4 3 2 1 0.5 1 2 3 4 5];
y = [0 0.25 0.75 1.5 2 2.5 3 3.5 4.5 4.75 5];
x_err = [0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5];
y_err = [0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5];
hold on
patch([x+x_err fliplr(x-x_err)], [y+y_err fliplr(y-y_err)],[0.8 0.8 0.8])
errorbar(x,y,-y_err,y_err,-x_err,x_err,'-')

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1 Answer

Answer by Subhadeep Koley on 5 Sep 2019

Since you want to shade the area between the four bounds for each point, the following code might help you.
% Demo data
x = [5 4 3 2 1 0.5 1 2 3 4 5];
y = [0 0.25 0.75 1.5 2 2.5 3 3.5 4.5 4.75 5];
x_err = [0.25 0.25 0.25 0.25 0.25 0.25 0.25 0.25 0.25 0.25 0.25];
y_err = [0.25 0.25 0.25 0.25 0.25 0.25 0.25 0.25 0.25 0.25 0.25];
hold on;
% Plotting errorbar
errorbar(x,y,-y_err,y_err,-x_err,x_err,'-','LineWidth', 2);
% Plotting shaded area
for i=1:numel(x)
x_i=[x(i),x(i)+x_err(i),x(i),x(i)-x_err(i)];
y_i=[y(i)+y_err(i),y(i),y(i)-y_err(i),y(i)];
patch(x_i,y_i,'green','FaceAlpha',.2);
end
hold off;
SK_errorbar.png

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