Plot scatter plot as shade

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Shahriar Mahmud 2021-10-21

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1569148-plot-scatter-plot-as-shade

评论： Star Strider 2021-11-17

Hi,

I have the attached data (conc.mat) where each row corresponds to y axis value for a given x value(t=[0;30;60;120;300;600;900]). I am doing uncertainty analysis here. I also have the actual data set (single y value for single x value), which should construct a firm plot in the same graph. So, in summary, I should have a firm line from the actual data set which I have not shared here, but also I should be able to generate a shaded area from the attached data. The final product should be something like the attached file (Capture.JPG). Please suggest some solutions. Thanks.

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Star Strider 2021-10-22

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1569148-plot-scatter-plot-as-shade#answer_813838

Try this —

LD = load('conc.mat');
conc = LD.conc;
t=[0;30;60;120;300;600;900];
figure
plot(t, conc)
hold on
shadeWidth = 0.01;
patch([t; flipud(t)], [min(conc,[],2)-shadeWidth; flipud(max(conc,[],2))+shadeWidth], [1 1 1]*0.5, 'FaceAlpha',0.25, 'EdgeColor','none')
hold off

Experiment to get different results.

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Star Strider 2021-10-27

I do not understand.

The data in the file are plotted correctly, and the shaded portion extends from a given distance below the lowest data to the same distance above the highest data.

To plot it around the mean instead —

patch([t; flipud(t)], [mean(conc,2)-shadeWidth; flipud(mean(conc,2))+shadeWidth], [1 1 1]*0.5, 'FaceAlpha',0.25, 'EdgeColor','none')

or the median —

patch([t; flipud(t)], [median(conc,2)-shadeWidth; flipud(median(conc,2))+shadeWidth], [1 1 1]*0.5, 'FaceAlpha',0.25, 'EdgeColor','none')

Those vectors are directly derived from the data, and the ‘shadeWidth’ is constant for the entire line. It may not appear to be constant because ‘shadeWidth’ is plotted in the ‘y’ direction, and that will appear different in the first part of the curve where the slope is greatest than in the last part of the curve where the slope is least. It is neverhteless the same throughout the curve.

Consider a sine curve —

x = linspace(-pi, pi);

s = sin(x);

figure

plot(x,s,'-r')

hold on

patch([x flip(x)], [s-0.1 flip(s)+0.1], 'b', 'FaceAlpha',0.25)

hold off

grid

xlim([min(x) max(x)])

The difference between the curves is the same throughout, however the shading appears to be thicker at the extreme ‘y’ values than it does near 0.

Shahriar Mahmud 2021-11-17

pchip.JPG

Thanks again.

It looks ok to me for the time being.

Please see attached. As you can see the shaded portions created by the patch function (See code above you suggested) needs to be smoothened as well. Any suggestions?