Shading area between 2 curves (x function in terms of y)
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rezheen
el 25 de Jun. de 2025
Hello, I'm trying to shade an area between two functions (x depending on y), I shade the correct area but I get a reflection of that shaded region possibly about the line y=x. I don't want this reflection in my graph, I only want the shaded region. Here's my code:
syms x y
x1=y^2; x2=y^3; y1=0; y2=1; % y1 & y2 are the boundaries
fp1 = fplot(x1, [y1 y2]); hold on; grid on;
fp2 = fplot(x2, [y1 y2]);
ylim('padded')
x1 = fp1.XData;
y1 = fp1.YData;
x2 = fp2.XData;
y2 = fp2.YData;
patch([y1 fliplr(y2)], [x1 fliplr(x2)], 'g'); hold off;
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Paul
el 25 de Jun. de 2025
Movida: Paul
el 25 de Jun. de 2025
Here are the plots of the functions. The independent variable is y, which spans the x-axis on the fplot
syms x y
x1=y^2; x2=y^3; y1=0; y2=1; % y1 & y2 are the boundaries
fp1 = fplot(x1, [y1 y2]); hold on; grid on;
fp2 = fplot(x2, [y1 y2]);
ylim('padded')
xlabel('y')
ylabel('x')
To shade the region in between we have to note that the xdata is actually the YData of the plot and the ydata is actually the XData of the plot, because we are plotting x = f(y);
figure
fp1 = fplot(x1, [y1 y2]); hold on; grid on;
fp2 = fplot(x2, [y1 y2]);
ylim('padded')
xlabel('y')
ylabel('x')
%x1 = fp1.XData;
%y1 = fp1.YData;
%x2 = fp2.XData;
%y2 = fp2.YData;
y1 = fp1.XData;
x1 = fp1.YData;
y2 = fp2.XData;
x2 = fp2.YData;
patch([y1 fliplr(y2)], [x1 fliplr(x2)], 'g'); hold off;
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Paul
el 30 de Jun. de 2025
I don't understand what you want to do for the three-curve case. How should y3 = 2 influence the result?
Más respuestas (2)
the cyclist
el 25 de Jun. de 2025
Editada: the cyclist
el 25 de Jun. de 2025
I think you got yourself -- and me -- confused by swapping the definitions of what are conventionally called the X- and Y-axis.
Is this what you want? Or did you want the lower one?
syms x y
% Note that I changed the function definitions in this line
x1=y^(1/2); x2=y^(1/3); y1=0; y2=1; % y1 & y2 are the boundaries
fp1 = fplot(x1, [y1 y2]); hold on; grid on;
fp2 = fplot(x2, [y1 y2]);
ylim('padded')
x1 = fp1.YData; % In these lines, you need to be careful that MATLAB calls
y1 = fp1.XData; % the horizontal axis "X", but that is what you call "Y".
x2 = fp2.YData;
y2 = fp2.XData;
patch([y1 fliplr(y2)], [x1 fliplr(x2)], 'g'); hold off;
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the cyclist
el 29 de Jun. de 2025
Editada: the cyclist
el 30 de Jun. de 2025
Another (I think simpler) method is to change the "view" of the axes.
This way the XData and YData properties of line up with what you expected. If you label your axes -- which you should -- then those do need to be swapped (because of the view change).
syms x y
x1=y^2; x2=y^3; y1=0; y2=1; % y1 & y2 are the boundaries
fp1 = fplot(x1, [y1 y2]); hold on; grid on;
fp2 = fplot(x2, [y1 y2]);
xlim('padded')
x1 = fp1.XData;
y1 = fp1.YData;
x2 = fp2.XData;
y2 = fp2.YData;
patch([x1 fliplr(x2)],[y1 fliplr(y2)],'g');
xlabel("y")
ylabel("x")
view([90 -90])
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