plot standard deviation as a shaded area

Hey,

I have a vector containing the mean values and a another vector with the standard deviations. I want to plot the standard deviation as a shaded area and the mean as a line as shown on the image below but I want to write my own function. hope someone can help

[M]

I want to write my own function

Does this mean you do not want to use built-in function like fill or area ?

You can start by reading this discussion:

https://mathworks.com/matlabcentral/answers/180829-shade-area-between-graphs

[Hinna Ahmed]

I want to use built-in functions like fill or area but not functions like stdshade because they use a matrix with all the observations as a input but i have already calculated the mean and std.

Answer 1

[M]

You can use the code directly from this answer:

https://mathworks.com/matlabcentral/answers/180829-shade-area-between-graphs#answer_169649

y = rand(1,10); % your mean vector;
x = 1:numel(y);
std_dev = 1;
curve1 = y + std_dev;
curve2 = y - std_dev;
x2 = [x, fliplr(x)];
inBetween = [curve1, fliplr(curve2)];
fill(x2, inBetween, 'g');
hold on;
plot(x, y, 'r', 'LineWidth', 2);

[Baldvin]

Here's the a similar code as above, using Patch and its properties. Hopefully, the variable names are descriptive:

% Dummy data:
x = linspace(-2,2,64);
meanCurve = 2 + x.^2 + 0.55*rand(size(x));
upperCurve = meanCurve + 0.5*abs(randn(size(x))) + 1;
lowerCurve = meanCurve - 0.5*abs(randn(size(x))) - 1;

% Create shaded area. We just have to create x/y points that trace out the 
% bottom curve from left to right, followed by the upper curve from right to left:
areaX = [x, fliplr(x)];
areaY = [lowerCurve, fliplr(upperCurve)];
shadedArea = patch("XData",areaX, "YData",areaY, ...
    "FaceColor",'flat',"EdgeColor",'flat',"SeriesIndex",2, ...
    "FaceAlpha",0.2, "EdgeAlpha",1);
% Add the curve:
hold on
meanLine = plot(x, meanCurve, "SeriesIndex",2, "LineWidth", 2);

●

[Star Strider]

This works for row vectors:

areaX = [x, flip(x)];

areaY = [lowerCurve, flip(upperCurve)];

For column vectors, use:

areaX = [x; flip(x)];

areaY = [lowerCurve; flip(upperCurve)];

NOTE -- The flip function will flip a vector appropriately. Use flipud or fliplr if you are working with matrices. (Using fliplr on a column vector does nothing useful!)

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