Is there a way to get shaded error regions on a scatter plot?

Hi folks,

I have a scatter plot with known errors for each datapoint. Is there a way to create a shaded region around the scatter plot? Below is my graph, the red and cyan regions are the errors and the blue is the data. Is there a way to shade them and make them a continuous line, like the graph below?

I've attached the table below, along with my code.

Thanks

figure;
hold on;
scatter(myData.Anisotropic_1, myData.AnisoMin);
scatter(myData.Anisotropic_1, myData.AnisoMax);
scatter(myData.Anisotropic_1, myData.("MPC aniso"), 'b');
alpha(0.1);

title('Axiovision versus MPC, with reproducibility (r) in shaded region',"FontWeight","bold");
xlabel('Axiovision', "FontWeight","bold");
ylabel('MPC', "FontWeight","bold");
hold off;

[Image Analyst]

Yeah, probably. https://matlab.fandom.com/wiki/FAQ#How_do_I_shade_the_region_between_two_curves?

If you have any more questions, then attach your data and code to read it in with the paperclip icon after you read this:

TUTORIAL: How to ask a question (on Answers) and get a fast answer

[Teshan Rezel]

@Image Analyst thanks, I've updated the post with my code and the relevant data!

Answer 1

[Star Strider]

It would help to have the data.

Try something like this —

x = linspace(0, 2*pi, 50);
y = sin(x) + 0.5;
err = rand(size(x))*0.5 + 0.5;

figure
scatter(x, y, 'filled')
hold on
patch([x, flip(x)], [y-0.25 flip(y+err)], 'b', 'FaceAlpha',0.25, 'EdgeColor','r', 'LineStyle','-.', 'MarkerSize',20)
hold off
grid

Experiment to get the desired result.

.

[Teshan Rezel]

@Star Strider Hi, unfortunately, this doesn't seem to work for me. May I ask what I might be doing wrong please?

xfill = [myData.Anisotropic_1 fliplr(myData.Anisotropic_1)];
obs_anisofill = [myData.AnisoMax fliplr(myData.AnisoMin)];

figure;
hold on;

% fill(xfill, obs_anisofill);
% plot(myData.Anisotropic_1, myData.AnisoMin);
% plot(myData.Anisotropic_1, myData.AnisoMax);
scatter(myData.Anisotropic_1, myData.("MPC aniso"), 'b');
h = lsline;
h.Color = 'b';
[p1, s1] = polyfit(get(h,'xdata'),get(h,'ydata'),1);
f1 = polyval(p1, myData.Anisotropic_1);
rs1 = my_Rsquared_coeff(myData.("MPC aniso"), f1);
caption1 = sprintf('y = %0.2fx + %0.2f, R^2 = %.2f', p1(1), p1(2), rs1);
text(min(myData.Anisotropic_1)+20, max(myData.("MPC aniso"))-40, caption1, 'FontSize', 10, 'Color', 'b', 'FontWeight', 'bold');
% plot(polyval(FitAniso, myData.Anisotropic_1));
patch(xfill, obs_anisofill, 'b', 'FaceAlpha',0.1, 'EdgeColor','r', 'LineStyle','-.', 'MarkerSize',20)

title('Axiovision versus MPC, with reproducibility (r) in shaded region',"FontWeight","bold");
xlabel('Axiovision', "FontWeight","bold");
ylabel('MPC', "FontWeight","bold");
hold off;

[Star Strider]

The vectors used for the patch call need to be sorted, since they are not originally. This sorts ‘myData.Anisotropic_1’ and then uses that index to reference the other vectors. Also, my code used row vectors, your uses column vectors, so that required a minor tweak. With those changes, it works.

Try this —

LD = load(websave('myData','https://www.mathworks.com/matlabcentral/answers/uploaded_files/1182658/myData.mat'));
myData = LD.myData

myData = 73×23 table
           Sample Name              Resin        All Coke     Anisotropic       Dark       Resin%    Coke%     Anisotropic_1    Dark_1    MPC aniso    MPC dark    Repeatability    AnisoMax    AnisoMin    DarkMax    DarkMin    CRI    Reflectance    Var19    Anisotropic_2    Dark_2    MPC aniso_1    MPC dark_1
    __________________________    __________    __________    ___________    __________    ______    ______    _____________    ______    _________    ________    _____________    ________    ________    _______    _______    ___    ___________    _____    _____________    ______    ___________    __________

    {'AFCO 16-OCT-18'        }    2.4344e+08    1.1445e+08    9.0583e+07     2.3872e+07     68.02     31.98       79.143        20.857      78.13       21.87         5.2079         84.351      73.935     26.065     15.649     NaN        NaN         NaN          NaN          NaN          NaN           NaN    
    {'Morfa float 27-01-21'  }    2.3271e+08    1.2519e+08    6.1369e+07     6.3817e+07    65.022    34.978       49.023        50.977      49.62       50.38         6.2992         55.322      42.723     57.277     44.678     NaN        NaN         NaN          NaN          NaN          NaN           NaN    
    {'Morfa sink 23-02-21'   }    2.4379e+08    1.1411e+08    7.8821e+07     3.5287e+07    68.117    31.883       69.076        30.924      67.97       32.03         5.8785         74.955      63.197     36.803     25.045     NaN        NaN         NaN          NaN          NaN          NaN           NaN    
    {'AFCO 3-APR-19'         }    2.3063e+08    1.2727e+08    7.7228e+07     5.0041e+07     64.44     35.56       60.681        39.319      62.28       37.72         6.1065         66.787      54.574     45.426     33.213     NaN        NaN         NaN          NaN          NaN          NaN           NaN    
    {'Morfa Float 24-02-21'  }    2.2987e+08    1.2803e+08    8.4423e+07     4.3603e+07    64.228    35.772       65.942        34.058      66.74       33.26         5.9359         71.878      60.006     39.994     28.122     NaN        NaN         NaN          NaN          NaN          NaN           NaN    
    {'Morfa Sink 30-01-21'   }    2.2898e+08    1.2892e+08    7.5212e+07     5.3708e+07    63.979    36.021        58.34         41.66      57.57       42.43         6.2268         64.567      52.113     47.887     35.433     NaN        NaN         NaN          NaN          NaN          NaN           NaN    
    {'Morfa Week 39 28-09-20'}    2.9123e+08    6.6666e+07    5.2124e+07     1.4542e+07    81.373    18.627       78.187        21.813      77.29       22.71         5.2784         83.465      72.908     27.092     16.535     NaN        NaN         NaN          NaN          NaN          NaN           NaN    
    {'MORFA FLOAT 09-NOV-21' }    2.9031e+08    6.7587e+07     4.511e+07     2.2476e+07    81.116    18.884       66.744        33.256      67.54       32.46         5.8991         72.643      60.845     39.155     27.357     NaN        NaN         NaN          NaN          NaN          NaN           NaN    
    {'MORFA FLOAT 31-OCT-21' }    2.7808e+08    7.9817e+07    4.5361e+07     3.4457e+07    77.698    22.302       56.831        43.169      55.63       44.37         6.2593          63.09      50.571     49.429      36.91     NaN        NaN         NaN          NaN          NaN          NaN           NaN    
    {'IJmuiden 50CRI'        }    2.2358e+08    1.3432e+08    6.8614e+07     6.5704e+07     62.47     37.53       51.083        48.917      50.68       49.32         6.2988         57.382      44.785     55.215     42.618     NaN        NaN         NaN          NaN          NaN          NaN           NaN    
    {'MORFA SINK 24-FEB-21'  }    2.2577e+08    1.3213e+08    8.7576e+07     4.4556e+07    63.081    36.919       66.279        33.721      67.28       32.72         5.9113          72.19      60.368     39.632      27.81     NaN        NaN         NaN          NaN          NaN          NaN           NaN    
    {'MORFA FLOAT 25-OCT-21' }    2.4612e+08    1.1177e+08    6.2124e+07      4.965e+07    68.769    31.231        55.58         44.42      56.38       43.62         6.2479         61.828      49.332     50.668     38.172     NaN        NaN         NaN          NaN          NaN          NaN           NaN    
    {'MORFA FLOAT 15-NOV-21' }    2.3216e+08    1.2574e+08    6.6332e+07     5.9408e+07    64.867    35.133       52.753        47.247      51.65       48.35          6.296         59.049      46.457     53.543     40.951     NaN        NaN         NaN          NaN          NaN          NaN           NaN    
    {'MORFA GROUND 2'        }    2.6764e+08    9.0259e+07     4.466e+07     4.5599e+07    74.781    25.219        49.48         50.52      47.38       52.62         6.2908          55.77      43.189     56.811      44.23     NaN        NaN         NaN          NaN          NaN          NaN           NaN    
    {'MORFA GROUND 3'        }    2.6259e+08    9.5305e+07    4.5938e+07     4.9368e+07    73.371    26.629       48.201        51.799       50.1        49.9         6.2994           54.5      41.901     58.099       45.5     NaN        NaN         NaN          NaN          NaN          NaN           NaN    
    {'MORFA GROUND 4'        }    2.5613e+08    1.0177e+08    6.4902e+07     3.6868e+07    71.564    28.436       63.773        36.227      61.37       38.63         6.1344         69.908      57.639     42.361     30.092     NaN        NaN         NaN          NaN          NaN          NaN           NaN    

[patchx,pidx] = sort(myData.Anisotropic_1);             % Sort, Return Index
patchy1 = myData.AnisoMax(pidx);                        % Use 'pidx'
patchy2 = myData.AnisoMin(pidx);                        % Use 'pidx'
xfill = [patchx; flipud(patchx)];
obs_anisofill = [patchy1; flipud(patchy2)];

figure;
hold on;
% % fill(xfill, obs_anisofill);
% % plot(myData.Anisotropic_1, myData.AnisoMin);
% % plot(myData.Anisotropic_1, myData.AnisoMax);
scatter(myData.Anisotropic_1, myData.("MPC aniso"), 'b');
h = lsline;
h.Color = 'b';
[p1, s1] = polyfit(get(h,'xdata'),get(h,'ydata'),1);
f1 = polyval(p1, myData.Anisotropic_1);
% rs1 = my_Rsquared_coeff(myData.("MPC aniso"), f1);            % 'my_Rsquared_coeff' Doesn't Exist
% caption1 = sprintf('y = %0.2fx + %0.2f, R^2 = %.2f', p1(1), p1(2), rs1);
% text(min(myData.Anisotropic_1)+20, max(myData.("MPC aniso"))-40, caption1, 'FontSize', 10, 'Color', 'b', 'FontWeight', 'bold');
% plot(polyval(FitAniso, myData.Anisotropic_1));
patch(xfill, obs_anisofill, 'b', 'FaceAlpha',0.1, 'EdgeColor','r', 'LineStyle','-.', 'MarkerSize',20)
title('Axiovision versus MPC, with reproducibility (r) in shaded region',"FontWeight","bold");
xlabel('Axiovision', "FontWeight","bold");
ylabel('MPC', "FontWeight","bold");
hold off;

Some information (‘rs1’) is missing, so I commented it out and the lines using it out so the rest of the code will run.

Make appropriate changes to get the desired result.

.

[Walter Roberson]

The alternative to sorting is to use boundary() with an alpha value to find the outline of the containing shape.

[Star Strider]

I’ve done that in the past, especailly when the outline to be filled would not yield to sorting and remained essentially impossible to define. Here, sorting worked.